Turkey wants modernised versions of F-16 fighter jets for its ageing air force, but US Congress must approve any sale.

"The Biden administration strongly supports the package to both upgrade the existing F-16s and to provide new ones," Blinken told a press conference in Ankara.

But Blinken added he could not provide a "formal timeline" for approval and delivery.

It was Blinken's first visit to Turkey as secretary of state in a trip that was planned before a 7.8-magnitude earthquake on February 6, which has now killed nearly 45,000 people in Turkey and Syria.

The top US diplomat is due to hold talks with Turkish President Recep Tayyip Erdogan later on Monday in Ankara.

The United States, whose relations with Turkey have been strained in recent years, has been looking for ways to persuade Erdogan to ratify NATO membership applications by Finland and Sweden.

Finland and Sweden dropped decades of military non-alignment and applied to join the US-led defence alliance last year in response to Russia's invasion of Ukraine.

But Turkey has yet to ratify their applications and Ankara has opposed Sweden's refusal to extradite dozens of suspects that Turkey links to outlawed Kurdish militants and a failed 2016 coup.

On Monday, Turkish Foreign Minister Mevlut Cavusoglu dismissed any attempt to apply conditions to the F-16 jets approval.

"It would not be right to make Sweden and Finland's NATO membership a condition for the F-16s. They are two different issues," he said. "Our hands should not be tied."

Blinken said the United States "strongly" supported Finland and Sweden's admission into NATO "as quickly as possible".

"Finland and Sweden have already taken concrete steps" to address Turkey's concerns, he said.

Turkey has signalled it is ready to accept Finland into NATO, but Cavusoglu said Kurdish militants continued "all kinds of activities including recruitment, terrorist propaganda" in Sweden.

Blinken arrived on Sunday at Incirlik air base in southern Turkey, through which the United States has shipped aid after the earthquake. The United States has now contributed $185 million in assistance to Turkey and Syria.