BEIRUT, Nov 3 (Reuters) - A senior U.S. official met Syria's national security chief in Damascus this week in the highest ranking visit to Syria by a U.S. official since the start of the war in 2011, a senior regional official close to Damascus told Reuters on Friday.

The Lebanese newspaper al-Akhbar first reported the visit earlier on Friday, saying that the U.S. official discussed security matters including Americans missing in Syria. Among them are operatives of the Central Intelligence Agency (CIA).

The regional official did not name the U.S. official who met Ali Mamlouk, Syria's national security chief. "It is an important step, but Damascus does not have confidence in the American position," the regional official said.

The U.S. official traveled to Damascus via Lebanon.

The United States has supported the opposition to President Bashar al-Assad during the Syrian war. It has provided anti-Assad rebels with weapons via a CIA-run military aid program that President Donald Trump ordered shut down earlier this year.

U.S. Secretary of State Rex Tillerson last week reiterated the U.S. position that Assad should leave power, saying the "reign of the Assad family is coming to an end" and "the only issue is how that should be brought about".

With military backing from Russia and Iran, Assad has recovered control of swathes of lost Syrian territory over the last two years and appears militarily unassailable.

U.S. forces have been fighting in Syria as part of the coalition against Islamic State, helping Kurdish-led militias capture Raqqa and other parts of northern and eastern Syria.

During the meeting, Mamlouk protested to the U.S. official that U.S. forces "are on Syrian land and this is considered occupation", the regional official said.

The U.S. official responded that "our presence is advisory and we are fighting Daesh", the regional official added, using an Arabic acronym for Islamic State. Syrian government officials could not immediately be reached for comment.