WASHINGTON, Dec. 12 (Xinhua) -- The U.S. Senate on Wednesday voted to open debate on a resolution calling for ending U.S. backing for the Saudi-led attack in Yemen, as the killing of Saudi journalist Jamal Khashoggi continues to strain ties between the Trump administration and the Congress.

The Senate voted 60-39 to open debate on the resolution, which was sponsored by Republican Senator Mike Lee and independent Senator Bernie Sanders, signaling an increasingly bipartisan notion to review Saudi Arabia's role in Khashoggi's death and the Yemen conflict, as well as bilateral relations as a whole.

However, it remained uncertain how the amendments to the resolution would influence the final vote, which could come later.

Bob Corker, Senate Foreign Relations Committee chairman, told media that he was preparing a separate resolution condemning the journalist's death. Senate majority leader Mitch McConnell urged senators to vote for Corker's proposal.

The two resolutions, if passed, would represent a bold challenge to the Trump administration, which has said that there is no smoking gun that proves Saudi crown prince's direct involvement in Khashoggi's death, hence has been reluctant to further punish the kingdom, in spite of the U.S. intelligence's conclusion on the involvement of the Saudi leader in the case.

The tragedy has also further intensified the Hill's outrage over the heavy civilian casualties caused by the Saudi-led attack in Yemen.

U.S. Secretary of State Mike Pompeo and Secretary Defense James Mattis are set to brief the full House on Khashoggi's case and the Yemen conflict on Thursday.

Khashoggi has been missing since he entered the Saudi consulate in Istanbul on Oct. 2. The Saudi authorities said he died in a "brawl" in the consulate, and denied that the Saudi crown prince had ordered the killing.