Europe's top diplomat Kaja Kallas was heading to Damascus on Monday, after a number of countries, including the United States, announced they had made initial approaches.
The situation in Syria, long allied with Iran and Russia, remains volatile and Western nations are wary of the Al-Qaeda roots of Hayat Tahrir al-Sham (HTS) that seized power in a lightning offensive.
But none wants to pass up the opportunity to forge links, given the risk of fragmentation and resurgence of the Islamic State group, which has never been completely eradicated.
"The first reaction of the West has without a doubt been to say that they don't meet terrorists," said Denis Bauchard, from the French Institute of International Relations.
HTS, which has its roots in Al-Qaeda, maintains it has renounced jihadism yet remains proscribed as a terrorist group by several Western countries, including the United States.
"But there's a political reality... and clearly a race to establish contact the fastest," added Bauchard, a former ambassador.
"The main objective," he added, is that Syria does not fall into "total chaos".
As well as Brussels and Washington, Paris plans to send a diplomatic mission to Damascus from Tuesday, to "retake possession" of French real estate and make "initial contact" with the new authorities.
Spain is to appoint a special envoy while the UK has announced that diplomatic contacts have been established with HTS.
Respectability
"Europeans waited for the American reaction, which encouraged them to take the step," said Hasni Abidi, director of the Study and Research Centre for the Arab and Mediterranean World in Geneva (CERMAM).
The approach was "pragmatic" while the Syrian people welcomed the rebels, he added.
"It was necessary to be among the first to show the Europeans' willingness to help the Syrian people" and to have "a position of choice by offering not legitimacy but a certain respectability to HTS which has de facto authority status".
Diplomats are not hiding the difficulties, with Syria at risk of fragmentation and from hard-line Islamists, the outgoing French Foreign Minister Jean-Noel Barrot said in Brussels Monday.
In his first comments since his flight from Damascus, Bashir al-Assad said on Monday that Syria was now "in the hands of terrorists".
He also insisted he had not planned to leave when the rebels took the capital and that his evacuation from the city was requested by Moscow.
Europe has several levers at its disposal, including financial reconstruction aid and the eventual lifting of sanctions to push Syria's new authorities towards a political transition acceptable to the West.
Britain's foreign minister David Lammy on Sunday said London had "diplomatic contact" to ensure that a "representative government" is established and stocks of chemical weapons secured.
Volker Perthes, from the German Institute for International and Security Affairs (SWP), said this weekend that it was in everyone's interest to back a "UN-supported but Syrian-owned political process" for inclusive government.
Limit Turkish influence
Europe's Kallas last week said there should be no repeat of the "horrific scenarios" of sectarian violence and the resurgence of extremists in Iraq, Libya and Afghanistan.
Western leaders are wary of how the Taliban presented a more moderate front until they took over Kabul in August 2021.
But Abidi said: "Every state has its own agenda, prerogatives and concerns".
The four French diplomats expected in Damascus on Tuesday will try to "sound out the new leaders" on the potential jihadist threat to French national security, he added.
About 100 French people are among the radical Islamist groups that toppled Assad in Syria and have been living in the rebels' northwestern stronghold of Idlib for years.
"On the US side, we are mainly concerned about what the relationship will be with Israel," said Bauchard.
Another major challenge for the West will be to stop President Recep Tayyip Erdogan's Turkey, which sees a chance to push the Kurds away from its border with the support of Syrian factions, from being the only interlocutor in Damascus.
