US Secretary of State Antony Blinken said Saturday that American officials have been in direct contact with the Syrian rebel group that spearheaded the overthrow of President Bashar Assad's government but is designated a foreign terrorist organization by the United States and others.

Blinken is the first US official to publicly confirm contacts between the Biden administration and Hayat Tahrir al-Sham, or HTS, which led a coalition of armed opposition groups that ousted Assad from power last Sunday.

Speaking at a news conference in Aqaba, Jordan, Blinken would not discuss details of the contacts but said it was important for the US to convey messages to the group about its conduct and how it intends to govern in a transition period.

“Yes, we have been in contact with HTS and with other parties,” Blinken said. He added that “our message to the Syrian people is this: We want them to succeed and we're prepared to help them do so”.

HTS, which was once an affiliate of al-Qaida, has been designed as a foreign terrorist organisation by the State Department since 2018. That designation carries with it severe sanctions, including a ban on the provision of any “material support” to the group or its members. The sanctions do not, however, legally bar US officials from communicating with designated groups.

HTS has worked to establish security and start a political transition after seizing Damascus and has tried to reassure a public both stunned by Assad's fall and concerned about extremist jihadis among the rebels. Insurgent leaders say the group has broken with its extremist past.

The group's leader, Ahmad al-Sharaa, formerly known as Abu Mohammed al-Golani, appeared in a video message Friday congratulating “the great Syrian people for the victory of the blessed revolution”.

US officials say Sharaa has been making welcome comments about protecting minority and women's rights but remain sceptical that he will follow through on them in the long run.

On Friday, the rebels and Syria's unarmed opposition worked to safely turn over to US officials an American man who had been imprisoned by Assad.