White House advisers recommended on Wednesday that US President Donald Trump veto a resolution to end Washington's support for the Saudi Arabia-led military campaign in Yemen.

The White House statement of administration policy came as the US Senate prepared to vote on the matter, one of several efforts by lawmakers to push Trump to toughen his policy toward the kingdom.

Backers of the resolution, who include some of Trump's fellow Republicans as well as Democrats, said they are optimistic about its chances of passing the Senate.

However, the Senate's Republican majority leader, Mitch McConnell, denounced the war powers resolution on Wednesday as he opened the Senate, calling it "inappropriate and counterproductive."