US Defence Secretary Mark Esper met Prince Khaled Bin Salman, Saudi Arabia’s deputy defence minister, on Monday on the first day of his visit to Riyadh.
The meeting comes at a time of rising tension between Washington and Tehran.
During the meeting, Mr Esper and Prince Khaled reviewed Saudi-US relations and aspects of strategic and military co-operation between the two countries, Saudi state news agency Spa reported.
The two also discussed and reviewed challenges, threats, common security and defence issues.
Prince Khaled met Mr Esper in August at the Pentagon, where the US official called the US-Saudi Arabian relationship “one of the most enduring” in the Middle East.
During his first visit to the kingdom, Mr Esper is likely to meet Saudi King Salman and Crown Prince Mohammed bin Salman.
On landing in Riyadh on Monday, he met the head of US Central Command, which is responsible for military operations in the Middle East and Afghanistan.
US-Iran tensions have risen to new highs since May 2018, when the Trump administration withdrew from an international accord that put limits on Tehran's nuclear programme in exchange for easing sanctions.
On October 11, the Pentagon said it was sending more US troops to Saudi Arabia after Riyadh asked for reinforcements.
That came after September 14 drone and missile attacks on Saudi oil plants, which Washington blames on Iran.
Iran has responded apprehensively to previous US troop deployments this year. But Riyadh and Tehran have shown a willingness to talk.
Iran last week urged regional powers to use diplomacy to reduce tensions, including Yemen's war, but cautioned that an Iranian tanker damaged in the Red Sea had been hit by rockets and there would have to be consequences.
On Sunday, the Pentagon chief was in Kabul on an unannounced visit to meet US troops and Afghan President Ashraf Ghani.
Mr Esper’s visit came amid deep uncertainty about the fate of the US military mission in Afghanistan after talks between Washington and the Taliban collapsed.