There is an urgent need to find a political solution to Yemen's war, US Defense Secretary James Mattis told Saudi Crown Prince Mohammed bin Salman on Thursday, as he voiced hope for a UN special envoy's peace efforts.

Since March 2015, Riyadh has led a bombing campaign in Yemen to push Houthi rebels out of the capital and reinstall the government of Abd Rabbuh Mansour Hadi.

"We must also reinvigorate urgent efforts to seek a peaceful resolution to the civil war in Yemen and we support you in this regard," Mattis said.

Dubbed by UN officials as the world's "largest man-made humanitarian crisis", Yemen has witnessed a massive cholera outbreak, shortages in basic needs and more than 10,000 deaths.

Asked by reporters at the start of his talks whether he would raise the issue of civilian casualties in Yemen, Mattis said: "We are going to end this war, that is the bottom line. And we are going to end it on positive terms for the people of Yemen, but also security for the nations in the peninsula."

Earlier this year, UN chief Antonio Guterres appointed former British diplomat Martin Griffiths as his new envoy charged with trying to broker peace in Yemen.

Will Picard, executive director of Yemen Peace Project, a Washington-based advocacy group, called Mattis statement "empty rhetoric".

"We heard from the beginning of the war US officials saying they want to put an end to the war, yet they keep perpetuating it," Picard told MEE.

'We must also reinvigorate urgent efforts to seek a peaceful resolution to the civil war in Yemen and we support you in this regard,' Mattis told bin Salman (AFP) Mattis praised Saudi Arabia for the "significant amounts of humanitarian aid" it had provided to civilians in Yemen. The Saudi-led coalition said earlier this year it would commit $1.5bn in humanitarian aid for the country.

Critics say Saudi aid in the shadow of the coalition’s blockade on Yemen exclusively puts the response to the humanitarian crisis in the hands of an active party in the conflict and does not reach Houthi-controlled territory.

The war in Yemen has displaced more than 2 million people and driven the country - already the poorest on the Arabian Peninsula - to the verge of widespread famine.

On Tuesday, the US Senate killed a resolution seeking an end to Washington's support for Saudi Arabia's campaign in Yemen.

Ending American military involvement in this conflict is crucial to ending the war in whole. -Will Picard, Yemen Peace Project

During the Senate debate before the vote, some backers called the three-year-long conflict in Yemen a “humanitarian catastrophe”, which they blamed on the Saudis.

Mattis had lobbied Congress to reject the bill, warning that restrictions could increase civilian casualties, jeopardise counterterrorism cooperation, and "reduce our influence with the Saudis".

The United States provides refuelling and intelligence support to the Saudi-led coalition.

Picard said the legislation would have been an important step towards peace.

"Ending American military involvement in this conflict is crucial to ending the war in whole," he said. "The United States cannot play a useful role in bringing peace to Yemen while it continues to be a belligerent in this conflict and to support the coalition's war efforts."

Pentagon spokeswoman Dana White said that during the meeting, the crown prince talked about increasing cooperation with the US military, including training.

President Donald Trump gave a warm welcome to the crown prince during a meeting at the White House earlier this week and credited US defence sales to Saudis with boosting American jobs.

Picard noted that Thursday's comments were not made by the secretary of state "because the US doesn't have one".

Trump sacked Rex Tillerson last week, and his new appointee, Mike Pompeo, has not yet been confirmed by the Senate.

Who is Martin Griffiths, UN's new envoy to Yemen? Read More »

"That vacuum at the top of America's diplomatic apparatus tells you all that you need to know about Trump administration's commitment to the peace process in Yemen," Picard said.

The Pentagon said Mattis and the crown prince also discussed Afghanistan, and Riyadh was willing to help members of the Taliban and their families who were interested in reconciliation efforts.

White said the Saudi crown prince was "quite positive" that Gulf countries involved in a long-running dispute would be able to move past it.

Washington is keen to end the standoff between Qatar on one side and several other Arab nations, including Saudi Arabia, on the other. The rift has divided the Gulf Cooperation Council group of countries and hurt US-led efforts to maintain a strong front against Iran.

Meanwhile, the US formally approved defence contracts totaling more than $1bn with Saudi Arabia on Thursday.

The department confirmed it had green-lighted a $670m deal for anti-tank missiles, a $106m contract for helicopter maintenance and $300m for ground vehicle parts.

An official said the deals had been in the pipeline since Trump has announced more than $100bn in possible new contracts on a visit to Riyadh last year.

"This proposed sale will contribute to US foreign policy and national security objectives by helping to improve the security of a friendly country which has been, and continues to be, an important force for political stability and economic growth in the Middle East," the Defense Security Cooperation Agency said.