President Donald Trump in a letter to the Senate said he is rejecting a measure passed by Congress to end US involvement in the Saudi-led war in Yemen.

"I am returning herewith without my approval S.J. Res. 7, a joint resolution that purports to direct the President to remove United States Armed Forces from hostilities in or affecting the Republic of Yemen," Trump said on Tuesday.

"This resolution is an unnecessary, dangerous attempt to weaken my constitutional authorities, endangering the lives of American citizens and brave service members, both today and in the future."

 This is the second time president used veto during his presidency to reject a resolution from Congress. Previously he vetoed a measure from Congress revoking his declaration of a national emergency at the US-Mexico border.

The Saudi-led coalition has been engaged in the civil war in Yemen since March 2015, when it started to carry out airstrikes against the Houthi armed rebels at the request of Yemeni President Abd Rabbuh Mansur Hadi. 

The Yemeni civil war has claimed over 7,000 lives, while over 20 million people in Yemen are currently in need of humanitarian assistance, according to UN estimates.