The US Senate has voted to debate ending US support for the Saudi-led coalition's war in Yemen, amid growing resistance to the conflict.

After a behind-closed-doors update from Mike Pompeo and James Mattis, in which disappointment was the common theme, the Senate passed a resolution 63-37 to begin officially debating the matter on the floor.

A number of senators sought the vote, over US support for the war against Houthi rebels in Yemen as part of a pushback against Donald Trump's stance. At least 10,000 civilians have died in the conflict, which began in 2015.

The murder of journalist Jamal Khashoggi in the Saudi consulate in Istanbul in October has sparked outrage around the world and piled pressure onto Riyadh's royal family. But Mr Trump has dismissed a reported CIA assessment that is said to assert with "high confidence" that Crown Prince Mohammed bin Salman is linked to the killing of Khashoggi.

Lindsey Graham, the South Carolina Republican who is often strongly allied with Mr Trump, voted to move forward with the resolution and said he would insist on a briefing from CIA director Gina Haspel.

He even threatened to withhold his vote on key measures if that did not happen and declared: "I'm not going to blow past this."

“If you don't draw the line here, where do you draw the line?" he added.

Saudi officials have repeatedly denied that Crown Prince Mohammed is connected in any way to the murder, which Riyadh's public prosecutor has blamed on a "rogue" squad of kidnappers looking to take Mr Khashoggi - a critic of the royal family - back to Saudi Arabia.

“I am not going to be denied the ability to be briefed by the CIA, that we have oversight of, about whether or not their assessment supports my belief that this could not have happened without MbS knowing,” Senator Graham told reporters, using a shorthand for the Saudi crown prince's initials.

Secretary of State Pompeo stuck close to Mr Trump in speaking to reporters after the behind-closed-doors Senate briefing. “There is no direct reporting connecting the crown prince to the order to murder Jamal Khashoggi,” Mr Pompeo said, after he and Defence Secretary Mattis told senators that weakening US-Saudi ties over the killing would be a threat to national security.

Mr Trump has said that he does not want to risk millions of dollars in arms deals with Saudi Arabia over the killing, and has said that the CIA's assessment is not a conclusive view on the matter.

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"Whether he did or whether he didn’t, he denies it vehemently. His father denies, the king, vehemently," Mr Trump said recently. The CIA doesn’t say they did it. They do point out certain things, and in pointing out those things, you can conclude that maybe he did or maybe he didn’t," he said.

Senators are clear that they want to hear CIA officials views on the killing before a decision is made on a full US response to Mr Khashoggi's 2 October murder, being particularly angry that neither CIA Director Gina Haspel or Director of National Intelligence Dan Coats were present.

“MbS has not taken ownership of the death,” Senator Bob Corker, the Republican chairman of the Senate Foreign Relations Committee said after the briefing.

Children suffering from acute malnutrition in Yemen Show all 17 1 /17 Children suffering from acute malnutrition in Yemen Children suffering from acute malnutrition in Yemen Doctors take some blood of Yemeni Yousef Abdullah Bakhit Ali, 13, suffering from severe acute malnutrition. With ongoing and unending conflict in Yemen, humanitarian situation continues to deteriorate across the country Unicef/Huwais Children suffering from acute malnutrition in Yemen A doctor weighs Yemeni baby Yahya Hamoud Ali Al Huzef, 9 months suffering from malnutrition Unicef/Huwais Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal,12 years old and suffering from severe acute malnutrition. He arrives with his family at a Unicef supported treatment centre in a hospital in Sanaa Unicef/Huwais Children suffering from acute malnutrition in Yemen A doctor measures the arm of Yemeni Ali Mohammed Ahmed Jamal, 12, who is suffering from malnutrition at a treatment centre in a hospital in Sanaa Unicef/Huwais Children suffering from acute malnutrition in Yemen There are over 400,000 severely malnourished children in need urgent lifesaving assistance in Yemen Unicef/Abdulhaleem Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal is weighed Unicef/Huwais Children suffering from acute malnutrition in Yemen A doctor measures the arm of baby Yahya Hamoud Ali Al Huzef Unicef/Huwais Children suffering from acute malnutrition in Yemen Unicef are currently working to reach 275,000 malnourished children with critical life-saving supplies and care for over 5 million people with safe and clean water to stop the spread of life-threatening diseases Unicef/Huwais Children suffering from acute malnutrition in Yemen Yahya Hamoud Ali Al Huzef with his family in his house in the outskirts of the capital Sanaa Unicef/Huwais Children suffering from acute malnutrition in Yemen The country is on the brink of famine and children's chances of survival are becoming slimmer by the day Unicef/Abdulhaleem Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal has his arm measured Unicef/Huwais Children suffering from acute malnutrition in Yemen Unicef are currently working to provide nearly 1 million children with vaccines and healthcare Unicef/Huwais Children suffering from acute malnutrition in Yemen Doctors take some blood of Yemeni Yousef Abdullah Bakhit Ali, 13 years old suffering from severe acute malnutrition at a treatment centre in a hospital in the capital Sanaa on November 2, 2018. (Release obtained) With ongoing and unending conflict in Yemen, humanitarian situation continues to deteriorate across the country. There are over 400,000 severely malnourished children in need urgent lifesaving assistance in Yemen. The country is on the brink of famine and childrenâ€™s chances of survival are becoming slimmer by the day. UNICEF are working with partners around-the clock to save children suffering from malnutrition and disease. We are currently working to reach: â€¢ 275,000 malnourished children with critical life-saving supplies and care â€¢ Over 5 million people with safe and clean water to stop the spread of life-threatening diseases â€¢ Nearly 1 million children with vaccines and healthcare â€¢ 9 million people with emergency cash assistance to help families buy basic commodities so they can survive Â© UNICEF/UN0253367/ Huwais Unicef/Huwais Children suffering from acute malnutrition in Yemen Unicef are working with partners around-the clock to save children suffering from malnutrition and disease Unicef/Abdulhaleem Children suffering from acute malnutrition in Yemen Unicef are currently working to provide 9 million people with emergency cash assistance to help families buy basic commodities so they can survive Unicef/Huwais Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal is suffering from malnutrition Unicef Children suffering from acute malnutrition in Yemen On 31 October 2018 in Yemen, the Al Thawra Hospital in Hodeidah where children are being treated for severe acute malnutrition. UNICEF Regional Director for Middle East and North Africa Geert Cappelaere visited Yemen from 29 October through 1 November 2018. As of 30 October 2018, over 11 million children â€“ 80 per cent of all children in the country â€“ require humanitarian assistance, due to the impact of the ongoing conflict. Worsening years of underdevelopment, attacks against civilians and civilian infrastructure and lack of salary payments for most civil servants have pushed basic services for children to the brink. Children face food shortages, disease, displacement and an acute lack of access to basic social services. One out of three children in Yemen is at risk of acute malnutrition. Â© UNICEF/UN0253574/Abdulhaleem Unicef/Abdulhaleem

Addressing the possibility of a full Senate vote on ending US support for the war in Yemen, where millions are facing famine, Mr Pompeo argued the humanitarian crisis “would be a hell of a lot worse" without US involvement.

Mr Pompeo argued “all we would achieve from an American drawdown is a stronger Iran and a reinvigorated Isis and al-Qaeda in the Arabian Peninsula (AQAP)” before adding: “Try defending that outcome back home.”

Mr Mattis made the point the US is "seldom free to work with unblemished partners," according to an excerpt of his statement released by the Pentagon.

“Long-standing relationships guide but do not blind us. Saudi Arabia, due to geography and the Iranian threat, is fundamental to maintaining regional and Israeli security, and to our interest in Mid-East stability," he said.

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Republican Senate Majority Leader Mitch McConnell, in a rare moment of publicly disagreeing with the president, said there has to be “some kind of response” from the US on the matter.

Khashoggi worked for The Washington Post and was a green card holder for several years. He was a fierce advocate for amplifying regular Arab voices and wrote often about freedom of speech.

"What obviously happened, as basically certified by the CIA, is completely abhorrent to everything the United States holds dear and stands for in the world," Mr McConnell said.

"We're discussing what the appropriate response would be,” he noted.

The resolution to end American involvement in the Yemeni conflict was brought by Senators Bernie Sanders and Republican Mike Lee earlier in the year but initially fell short by just six votes.

Our support for the Saudi-led bombing campaign in Yemen has created a humanitarian crisis. Call your Senators and tell them to support S.J. Res. 54, my bill with @SenSanders and @SenMikeLee to end U.S. involvement in the war in Yemen. pic.twitter.com/VDTHONaEpJ