NEW YORK -- Heavy rain postponed all doubles matches and delayed the scheduled start of play for five hours at the U.S. Open on Thursday.

Third-seeded Jennifer Capriati and Tina Pisnik came on the court to begin warming up at 4 p.m. ET.

With the forecast calling for rain throughout the day the chances are slim that a ball will be struck, at least until much later in the day.

Rain is also forecast through Sunday, which would create quite a backlog as the tournament heads into its second week.

A steady drizzle Wednesday evening forced one match to be suspended and another to be postponed. Fourth seed Lindsay Davenport of the United States and Petra Mandula of Hungary had their second-round match delayed twice and finally suspended with Davenport leading, 6-4, 2-2.

"Given the weather forecast for the next few days, we made every effort to complete as much tennis as possible," said tournament director Jim Curley.

The second Wednesday night match between No. 25 James Blake of the U.S. and Russia's Nikolay Davydenko also was postponed.

Davenport and Mandula are scheduled to resume as the third match in Thursday's session at Arthur Ashe Stadium. The Blake-Davydenko match also is scheduled to be third Thursday in Louis Armstrong Stadium.

Top men's seed and defending champion Lleyton Hewitt of Australia is in action Thursday, weather permitting, along with sixth-seeded American Andre Agassi.

Hewitt will play Noam Okun and Agassi will face Justin Gimelstob in the second round.

Last year, Hewitt became the second youngest U.S. Open champion in the Open Era (1968-present) with his rout of Pete Sampras in the final and breezed to a straight-sets win over Nicolas Coutelot of France in the first round on Tuesday.

Hewitt has proved to be a worthy No. 1, tying for the ATP Tour lead with four titles, including his first Wimbledon crown.

Women's second seed and defending champion Venus Williams is scheduled to play Alicia Molik on Thursday night in a second-round match. Williams crushed Croatian qualifier Mirjana Lucic, 6-0, 6-0 in the first round.

Capriati matched Williams' performance Tuesday with a 6-0, 6-0 win over fellow American Bethanie Mattek.

Information from The Associated Press, SportsTicker and Reuters was used in this report.