The two men met at the Pentagon as part of Prince Mohammed's tour of the United States, which began this week with a White House visit.

"As you discussed with President (Donald) Trump on Tuesday, 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 Prince Mohammed.

Mattis said he believes Saudi Arabia is "part of the solution."

"They have stood by the United Nations-recognized government and 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," Mattis added.

Saudi Arabia leads a coalition in Yemen fighting the Iran-backed Huthi rebels.

The devastating three-year-old conflict was an early proving ground for the prince, who is also the minister of defense, but it has been beset by allegations of atrocities against civilians, and strategic drift.

Just hours after the prince left the White House on Tuesday, the US Senate rejected a bipartisan bid designed to curtail US support for the war, which includes air-to-air refueling of Saudi jets as well as target and intelligence sharing.

Speaking through a translator, Prince Mohammed told Mattis that cooperation between the Pentagon and the kingdom had "improved tremendously."

More than 9,200 people have been killed and tens of thousands wounded in Yemen's war, which is seen as both a civil conflict and a proxy war between regional titans Saudi Arabia and Iran.