A news conference due to be held by US diplomats in Syria following a meeting with the country’s new leadership has been cancelled due to “security concerns”, the US embassy has said.

A US official did not confirm what the concerns were, or whether the diplomats had met with the country’s new ruler, Ahmed al-Sharaa. They said a briefing would instead be held virtually later on Friday.

A short while later, the US military said it had killed an Islamic State (IS) leader in an air strike in Syria.

The US delegation arrived in the capital, Damascus, to meet with representatives from Hayat Tahrir al-Sham (HTS), which overthrew the Bashar al-Assad regime less than a fortnight ago but which Washington still designates a terrorist group.

The visit is the first formal American diplomatic appearance in Damascus in more than a decade.

It is a further sign of the dramatic shifts under way in Syria since the ousting of Assad, and the speed of efforts by the US and Europe, also leaning on Arab countries, to try to influence its emerging governance.

The visit follows those of delegations in recent days from the UN and other countries including the UK, France and Germany.

The delegation of senior officials includes Assistant Secretary of State Barbara Leaf, Roger Carstens, who is US President Joe Biden’s hostage envoy and Daniel Rubinstein, senior adviser in the Bureau of Near East Affairs.

“They will be engaging directly with the Syrian people, including members of civil society, activists, members of different communities, and other Syrian voices about their vision for the future of their country and how the United States can help support them,” a State Department spokesperson said in an earlier statement.

The meeting is a show of readiness to deal with HTS, which US still designates as a terrorist organisation but is building pressure for it to transition to inclusive, non-sectarian government.

Washington is effectively laying down a set of conditions before it would consider delisting the group – a critical step which could help ease the path towards sanctions relief that Damascus desperately needs.

The officials are seeking further information to help find the American journalist Austin Tice, who was abducted in Damascus in 2012.

Meanwhile, US Central Command (CENTCOM) confirmed that IS leader Abu Yusif and two of his operatives had been killed in an air strike in the Dayr az Zawr Province of north-eastern Syria.

It said in a statement on Friday that the airstrike was launched on Thursday and carried out in an area that was formerly controlled by the Assad regime and Russian forces supporting his government.

CENTCOM commander Gen Michael Erik Kurilla said the US would not allow IS “to take advantage of the current situation in Syria and reconstitute”, adding the group intended to free more than 8,000 detained IS militants being held in Syria.