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.

Relations between the United States and Turkey have been strained in recent years, but Washington has found Ankara helpful for its mediatory role between Russia and Ukraine since Moscow's invasion last year.

On Monday, Blinken held talks with President Recep Tayyip Erdogan, during which they discussed Ukraine and "the need to work more closely" on issues including defence, energy and collective security, State Department spokesman Ned Price said.

One of the main issues on the agenda of the visit has been Turkey's desire to buy modernised versions of F-16 fighter jets for its ageing air force.

The US Congress is blocking the sale due to concerns over Turkey's human rights record and threats to Greece.

"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.

- NATO applications -

The other main issue discussed during Blinken's visit is Turkey's refusal to ratify Sweden and Finland's NATO membership applications.

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.

Ankara has criticised 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 said no conditions should be applied 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."

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.

But the Turkish minister said suspended talks on their membership would resume in Brussels "in the near future", in comments welcomed by Stockholm.

Swedish Foreign Minister Tobias Billstrom told journalists in Brussels that Sweden was ready for talks, adding "this is a welcome and good announcement from Turkey".

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.

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.

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