Türkiye’s Parliament was set to resume talks Tuesday on ratifying Sweden’s NATO accession protocol, a thorny issue that has strained ties between Ankara and its allies since last year.

Sweden and Finland dropped decades of military non-alignment and sought to join the United States-led defense organization after Russia invaded Ukraine in February 2022.

Their bids won fast-track approval from all NATO members except Türkiye and Hungary. The two ultimately relented and Finland was accepted as NATO's 31st member in April.

Türkiye and Hungary remain the only NATO members left to ratify Sweden's bid 19 months after it applied for membership.

In November, the Turkish Parliament's foreign affairs committee failed to reach an agreement on a text for a full floor vote and will meet again on Tuesday afternoon.

President Recep Tayyip Erdoğan in July lifted his objections to Sweden’s NATO membership after Stockholm cracked down on members and sympathizers of the PKK, a terrorist group that has led a bloody campaign against the Turkish state since the 1980s, killing over 40,000 civilians.

"We see that there is a change in policy in Sweden. We see some decisions taken in courts, albeit few," Fuat Oktay, a lawmaker from Erdoğan's ruling Justice and Development Party (AK Party) and head of Parliament's foreign affairs committee said in a televised interview on Monday.

"We had some requests for further steps to be taken," he added.

Once it is approved by the committee, there will be a vote on the full Parliament floor, where Erdoğan's ruling alliance holds the majority of seats.

But the process is fraught with problems.

In December, Erdoğan suggested that Parliament will only act on Sweden if the U.S. Congress approves Türkiye's requested purchase of dozens of F-16 fighter jets and spare parts, and if other NATO allies including Canada lift arms embargoes imposed on Ankara.

"Positive developments from the United States regarding the F-16 issue and Canada keeping its promises will accelerate our Parliament's positive view (on Sweden's membership bid)," Erdoğan said.

"All of these are linked," he added.

"Sweden's NATO membership and F-16 sales to Türkiye will be handled in coordination to some extent ... because unfortunately, neither country trusts the other," Özgür Ünlühisarcıklı, the Ankara office director of the U.S. German Marshall Fund think tank, told Agence France-Presse (AFP).

In 2019, Ankara was excluded from the U.S.-led F-35 joint strike fighter program in retaliation for its decision to acquire an advanced Russian missile defense system that NATO views as an operational security threat.

U.S. President Joe Biden's administration has repeatedly promised to move forward with the $20 billion (TL 586.26 billion) F-16 sale but lawmakers have blocked it over what Türkiye calls "political motivations," including Ankara’s past tensions with Greece.

"There is no strong consensus in Parliament on Sweden's NATO membership, nor in the U.S. Congress on the sale of F-16s to Türkiye," Ünlühisarcıklı said.

Erdoğan's anti-Israel rhetoric after the start of its brutal attacks on the blockaded Gaza Strip in response to an incursion by Palestinian resistance group Hamas has also stoked concerns in Washington.

"Although the issues are not related, Türkiye's statements supporting Hamas further complicated the F-16 process," Ünlühisarcıklı said, adding that the killing of Turkish soldiers by PKK terrorists last weekend could also factor into Sweden's NATO membership.

"But if Biden and Erdoğan show the necessary will, we can expect the process to be concluded soon," he added.