Foreign countries have ramped up efforts to establish diplomatic contact with the new Syrian government, with the EU being the latest to confirm that it will send a delegation to Damascus.
The outreach from Brussels on Monday comes after the United States and Britain said they had made contact with the new authorities in Damascus, spearheaded by the Hayat Tahrir al-Sham (HTS).
Regional and international powers are jostling for influence in Syria after Assad was toppled in a lightning offensive, ending five decades of his family's rule.
"Our top diplomat in Syria will go to Damascus today. We'll have the contacts there," Kallas told journalists ahead of a meeting of EU foreign ministers.
EU nations – like others in the West – have some concerns over the new leadership in Damascus, over religious ideologies.
The EU cut ties with the Assad regime in Damascus during the country's civil war but has remained a major donor of humanitarian aid to help local populations.
Kallas said EU foreign ministers in Brussels would discuss "how we engage with the new leadership of Syria, and on what level we engage."
"We can't leave a vacuum," Kallas, who took over as the EU's top diplomat this month, said.
International players have expressed cautious optimism as the nascent Salvation Government in Damascus has vowed to protect minorities and form an inclusive government.
Diplomats say some EU member states are pushing to step up ties with Syria after Assad's ouster, while others are more cautious.
"For us, it's not only the words, but we want to see the deeds going to the right direction. So not only what they are saying, but also what they are doing," Kallas said.
"I think the coming weeks and months will show whether it goes to the right direction. And I think then we are also open to discuss next steps," she said.
Earlier Sunday, the United Nations special envoy for Syria was among those arriving in Damascus, where he pressed for "justice and accountability for crimes."
"And we need to make sure that that goes through a credible justice system, and that we don't see any revenge," Geir Pedersen said.
He later met HTS leader Abu Mohammed al-Golani, the group's Telegram channel said.
A Qatari delegation also landed in Syria to meet transitional government officials.
They reaffirmed the Gulf emirate's "full commitment to supporting the Syrian people ... following the success of their revolution," Qatar's Foreign Ministry spokesman told the emirate's official news agency.
Qatar's embassy is set to resume operations Tuesday, 13 years after it closed in the early stages of the anti-government uprising that turned into years of civil war.
Unlike other Arab countries, Qatar never restored ties with Assad's Syria.
Meanwhile, Türkiye, a major player in Syria's conflict, with considerable sway in the northwest, reopened its Damascus embassy on Saturday after 12 years.
Britain's foreign minister said London had established diplomatic contact with the HTS.
They remain "a proscribed terrorist organization, but we can have diplomatic contact and so we do have diplomatic contact," said David Lammy who also announced an aid package for Syrians.
Washington's top diplomat Antony Blinken said his country has also made "direct contact" with the HTS.
A French diplomatic team is due in Damascus on Tuesday to "retake possession of our real estate" as well as "establishing initial contact" with the new authorities, said acting Foreign Minister Jean-Noel Barrot.
They would also be "evaluating the urgent needs of the population," he added.
Russia, which propped up the Assad regime, said it had evacuated some of its diplomatic staff from Syria Sunday, "by a special flight of the Russian Air Force from the Hmeimim airbase" in Syria.
