ROME (Reuters) - Venus Williams's return from over a month on the sidelines with an unspecified medical problem was delayed on Tuesday as rain forced play to be abandoned at the Italian Open.

Only four matches were completed before organisers suspended play all together, with the seventh seed's second round match against Australian Samantha Stosur postponed until Wednesday.

The American's sister Serena also had her match against Ukrainian Alona Bondarenko bumped into Wednesday's schedule.

Russian world number two Maria Sharapova will start her Italian Open campaign on Wednesday against Dominika Cibulkova after the Slovak beat Argentine Gisela Dulko 7-6 6-4 in the first round.

Top seed Ana Ivanovic, who has a bye to the second round, will take on Bulgarian Tsvetana Pironkova, a 6-4 6-2 winner over fellow qualifier Klara Zakopalova of the Czech Republic.

Belarusian Victoria Azarenka cruised past Austrian 19th seed Sybille Bammer 6-1 6-3 to reach the second round, while Italian wildcard Roberta Vinci beat Estonian Kaia Kanepi 6-4 4-6 6-0.