The session follows a nonbinding vote in the House of Representatives, in which 17 Republicans joined the majority Democrats to oppose the rise in numbers.

Correspondents say Republicans could block a Senate vote, but Democrats will nevertheless be able to claim a moral victory.

Bush now faces battles with congress over funding for US troops in Iraq.

Although both the congressional resolutions are non-binding, the president needs the legislators to support his $93bn (Euro71bn) emergency troop-funding measure.

Yesterday's vote follows days of fierce debate, during which the Democrats have made it clear that more decisive steps to limit Bush's war policy could follow.