* Egyptian military allowing peaceful protests
* But soldiers spread out to tamp down any violence
* How army deals with trouble may determine aid to Cairo
By Alastair Macdonald and Alexander Dziadosz
CAIRO, July 5 (Reuters) - Islamist supporters of Egypt's ousted president, Mohamed Mursi, will rally on Friday to express their outrage at his overthrow by the army and to reject a planned interim government backed by their liberal opponents.
Dozens of people were wounded in clashes in Mursi's home city on Thursday, raising fears of more of the violence in which several dozen have died in the past month. There were also militant attacks in the restive Sinai peninsula, next to Israel.
How the army deals with trouble will help determine future support for Cairo from the United States and other international powers. Concern that the generals have carried out a military coup against Egypt's first-ever freely elected leader has left Washington reviewing the $1.5 billion in military and civilian aid it annually gives Egypt.
The planned protests have the slogan "Friday of Rejection".
A military source said: "We will continue to secure the places of protest with troops, and jets if necessary, to make sure the pro- and anti-Mursi demonstrators don't confront each other. We will let them demonstrate and go where they want."
Mursi's political opponents insist there was no coup. Rather, the army heeded the "will of the people" in forcing the president out. Millions rallied on Sunday to protest at a collapsing economy and political deadlock, in which Mursi had failed to build a broad consensus after a year in office.
After a busy day of diplomacy by concerned Obama administration officials interrupting their Independence Day holiday in Washington, the Egyptian armed forces command issued a late-night statement guaranteeing rights to protest and free expression and pledging not to pursue arbitrary measures against any political group.
The uncontroversial phrasing belied a busy 24 hours since the military chief suspended the constitution, detained Mursi and oversaw the swearing in of the chief justice of the constitutional court as Egypt's interim head of state.
In addition to Mursi, the country's first freely elected leader, several senior figures in his Muslim Brotherhood were arrested, security sources said. Prosecutors were investigating various charges, including incitement to violence and, in the case of Mursi himself, insulting the judiciary.
Television channels owned by or seen as sympathetic to the Brotherhood were unceremoniously taken off air. The state printer did not run off its party newspaper on Thursday.
In Zagazig, the Nile Delta city where Mursi has a family home, 80 people were injured. Witnesses said the army moved in to seal the area after an attack on pro-Mursi protesters by men on motorcycles led to clashes with sticks, knives and bottles.
For a movement that has been banned and politically oppressed for most of its 85-year history, such developments have reinforced impressions among the Islamists that a "deep state", once loyal to fallen autocrat Hosni Mubarak and his army-backed predecessors, is still determined to crush it.
The armed forces' longtime U.S. sponsor - which provides $1.3 billion in annual military aid - has voiced concern for human rights, but also for the stability of the biggest Arab nation. Egypt's peace with Israel and control of the Suez Canal give it a strategic importance for many beyond its 84 million people.
Washington, along with Middle Eastern allies from Israel to Saudi Arabia, are not lamenting the Brotherhood's stunning reversal. The organisation has long represented many Arabs' hopes for a better society but was found gravely wanting during Mursi's year of missteps and rancorous division.
The White House has avoided condemning Mursi's ouster as a "coup", a distinction that could trigger legal U.S. obstacles to aid. Some on Obama's national security team had contacted Egyptian officials "to convey the importance of a quick and responsible return of full authority to a democratically elected civilian government", it said.
In a statement on its Facebook page, the Egyptian military command said: "Wisdom, true nationalism and constructive human values that all religions have called for, require us now to avoid taking any exceptional or arbitrary measures against any faction or political current."
That appeared to be a response to concern internationally that, following Mursi's overthrow, there was a campaign of arrest and intimidation against the Brotherhood.
Egypt's caretaker Foreign Minister Mohamed Kamel Amr said that U.S. Secretary of State John Kerry had expressed concern during a telephone call on Thursday for human rights:
"He was worried about the status of human rights," Amr said. "Understandably. I assured him there is no retribution, no acts of vengeance, that nobody will be treated outside the law."
Amr, a career diplomat who tended his resignation to Mursi after Sunday's anti-government protests, said he had spent the day calling international counterparts and briefing ambassadors with the message that there had been no "military coup" in Egypt. The army had merely heeded the popular will.
Of his conversation with Kerry, he said: "I told him that the main aim of the military now is to maintain security.
"There will be no acts of violence, no acts of exclusion. Everybody will be included. The idea is to have everybody participating in the transitional process."
Those were also sentiments expressed by Adli Mansour, the constitutional court chief justice sworn in as interim head of state. But a senior Brotherhood official said it would not work with "the usurper authorities".
Another of its politicians said Mursi's overthrow would push other groups, though not his own, to violent resistance.
The armed forces' statement also contained a warning to those Islamists planning to demonstrate on Friday. It said: "Peaceful protest and freedom of expression are rights guaranteed to everyone, which Egyptians have earned as one of the most important gains of their glorious revolution."
That was a reference to fall of Mubarak, a key U.S. ally, in 2011 during the Arab Spring uprisings across the region.
But it added: "Excessive use of this right without reason could carry some negative implications, including blocking roads, delaying public benefits and destroying institutions, posing a threat to social peace, the national interest and damaging the security and economy in our precious Egypt."
Washington has been urging Egyptian leaders to resolve their differences quickly so that unrest which has sapped tourist revenue and investment ends and the economy can recover.
The Brotherhood renounced violence decades ago. Even among its allies who were engaged in armed struggle against Mubarak in the 1990s and beyond, there seems little appetite to resume it.
But Egypt does have troubles with militancy, not least in the largely empty Sinai peninsula, where radical Islamists with links to al Qaeda have become more active since Mubarak fell.
Early on Friday, security sources and state television said Islamist gunmen opened fire on El-Arish airport, close to the border with the Gaza Strip and Israel and at three military checkpoints. A police station in Rafah on the Gaza border was hit by rockets, wounding several soldiers.
It was not clear whether the coordinated attack on several army positions was in response Mursi's overthrow.
Mursi's dramatic exit was greeted with delight by millions of jubilant people on the streets of Cairo and other cities on Wednesday evening, but there was simmering resentment among Egyptians who opposed the military intervention.
Following the swearing in of Mansour as interim head of state, the next step in the army's road map back to democracy is the formation of an interim government in the next few days. One state newspaper said it should be ready on Sunday.
After that, a panel is to revise the constitution in order to hold parliamentary and presidential elections.
Amr Moussa, a former foreign minister, head of the Arab League and now liberal party leader, told Reuters he expected the full transition to elected institutions to take no more than 12 months and possibly just six. "This is doable," he said.
Analysts at Stratfor consultancy, however, highlighted tensions among the Brotherhood's opponents, whose fragmentation helped the movement defeat them in elections last year.
"It will be difficult," it said, "For the disparate blend of liberal, secular and Islamist parties united in their shared desire to see Morsi deposed to maintain their cohesion." (Reporting by Asma Alsharif, Mike Collett-White, Alexander Dziadosz, Seham El-Oraby, Shaimaa Fayed, Maggie Fick, Alastair Macdonald, Shadia Nasralla, Tom Perry, Yasmine Saleh, Paul Taylor, and Patrick Werr in Cairo, Abdelrahman Youssef in Alexandria and Yursi Mohamed in Ismailia; Writing by Alastair Macdonald; Editing by Philip Barbara)