The United States called Tuesday on all nations to think twice about rehabilitating Syria's "brutal" President Bashar al-Assad after his defense minister held a breakthrough meeting with Turkey.

Turkish President Recep Tayyip Erdogan, a key supporter of rebels seeking to topple Assad since 2011, has voiced openness to meeting the Syrian leader after rival neighbors' defense ministers met last week in Russia.

"We do not support countries upgrading their relations or expressing support to rehabilitate the brutal dictator Bashar al-Assad," State Department spokesman Ned Price told reporters.

"We urge states to carefully consider the Assad regime's atrocious human rights record of the past 12 years as it continues to inflict atrocities on the Syrian people and to deny access to life-saving humanitarian aid," Price said.

Assad, helped by Russian airpower, has largely restored control over Syria after the conflict that has killed half a million people, displaced half the country's pre-war population and saw the rise of the Islamic State extremist group.

With last year registering the lowest death toll since the conflict erupted, a growing number of countries have been accepting Assad as a victor. He flew in March 2022 to the United Arab Emirates, a US ally, in his first trip to another Arab state since the war.

Hoping to assuage the opposition, Turkey on Tuesday welcomed its leaders and reiterated support for a UN Security Council resolution that calls for a political settlement in Syria.

The United States, under the so-called Caesar Act that took effect in 2020, authorizes sanctions against Assad over war abuses and bars US support for reconstruction without accountability.