UPDATE 1-Tennis-Radwanska progresses on rainy day in Montreal

MONTREAL, Aug 9 (Reuters) - Agnieszka Radwanska's hope of

claiming the world's top ranking ahead of the U.S. Open remains

alive after she survived a testing first match in the Montreal

Cup on Thursday.

The Pole, who is seeded second in the Aug. 4-13 tournament,

will replace Victoria Azarenka as World No. 1 if she wins the $2

million event and the reigning Australian Open champion fails to

reach the quarter-finals.

Radwanska, who was stretched all the way by German Mona

Barthel on a day of upsets, came from a break down in the final

set to win 4-6 6-3 7-6 (5).

At least Radwanska, who plays Chanelle Scheepers in the

third-round, completed her match on a day marred by rain.

Azarenka will be forced to wait until Friday at the earliest

to finish her match against Tamira Paszek after it was postponed

on Thursday night due to rain.

The second round encounter is tied at 3-all in the opening

set.

Ana Ivanovic had a humbling start to her North American hard

court campaign as the former world number one failed to win a

game when thrashed in just 44 minutes by Italian Roberta Vinci.

"“I can't remember last time I had a match like this, you

know, maybe not since I was a junior," the 24-year-old Serbian,

who won this event in 2006, told reporters.

"“It's obviously tough, you know, but I just want to try and

put it behind me and try to forget about this because that's the

only thing you can do."

Her compatriot and 13th seed Jelena Jankovic, another former

world number one, fell for the first time in five meetings to

Canadian Aleksandra Wozniak 6-2 6-3.

American Varvara Lepchenko upset 12th seed Dominika

Cibulkova 6-4 6-4 in a rain-interrupted match and will play

either Caroline Wozniacki or Kiki Bertens on Friday. Wozniacki,

the 7th seed, leads 7-5 4-0 in the match still to be completed.

China's Li Na, the 10th seed, ended the hopes of Wozniak's

doubles partner and fellow Canadian Eugenie Bouchard 6-4 6-4

just before rain ended play for the day. She said the

conditions, which are expected to continue on Friday, made it

difficult for all the players.

"“It's really tough. I think I was warming up like a hundred

times," she said. "“You never know when you can come to court,

so you always have to ... stand up every second."

15th seeded Sabine Lisicki of Germany needed treatment from

the trainer during her 3-6 6-3 6-4 loss to Spaniard Carla Suarez

Navarro.

Ninth seed Marion Bartoli, who advanced on Thursday by

beating China's Peng Shuai 6-1 6-3, opens play on Friday against

former Wimbledon champion Petra Kvitova. Reigning US Open

champion Sam Stosur faces 16th seed Lucie Safarova on the second

stadium court.

(Editing by Daniel Magnowski)