efe-epaWashington DC

The president of the United States vetoed a resolution Tuesday passed by Congress calling on the US to withdraw military support for Saudi Arabia in the conflict in Yemen.

It was the second time during Donald Trump's presidency that he has vetoed a congressional motion.

"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," Trump said in a statement after he had vetoed the measure.

The president said the measure was unnecessary because, apart from counter-terrorism operations against al-Qaeda and against the Islamic State on the Arabian Peninsula, the US was not actively participating in hostilities in Yemen.

The president emphasized that there were no US troops "commanding, participating or accompanying" Saudi coalition forces fighting against Houthi rebels in Yemen.

It's the second time Trump has vetoed a congressional measure in his now more than two years in the White House. Last month he vetoed a motion which disapproved of his emergency declaration to erect barriers along the country's southern border.

The House of Representatives, which is controlled by the Democrats, passed the resolution on Yemen at the beginning of the month by 245 votes to 175, while the Senate did the same weeks earlier with 54 in favor and 46 against the motion.

Both the House and Senate would require two-thirds majorities to reverse Trump's veto.

The House's resolution called on Trump to end US military involvement in or "affecting" Yemen within 30 days, except for anti-terror operations against Al Qaeda.

The measure won the support of most representatives following the assassination of Saudi journalist Jamal Khashoggi on Oct. 2, 2018 at his country's consulate in Istanbul.

Khashoggi, who was a vocal critic of the Saudi government and monarchy and had been living in self-imposed exile in the United States, is widely assumed to have been killed by agents who were sent from the Saudi capital Riyadh, some of whom are allegedly close to the Crown Prince Mohammed bin Salman.

But Trump has defended Saudi Arabia as a major US ally in the region, rejecting calls to review his country's relationship with the oil-rich Gulf state following Khashoggi's alleged murder.

The US-backed Arab coalition, which has carried out numerous attacks on Yemen in which dozens of civilians have died, became involved in the conflict across their southern border in Mar. 2015 as the war intensified.

The United Nations said in February that the conflict, which has raged since the ouster of president Ali Abdullah Saleh during the Arab Spring uprising, has triggered the worst humanitarian crisis in the world.

"An estimated 24 million people – close to 80 percent of the population – need assistance and protection in Yemen", the UN said.