Sweden and Finland dropped decades of military non-alignment and sought to join the US-led defence organisation after Russia invaded Ukraine last year.

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

Turkey and Hungary remain the only North Atlantic Treaty Organization 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 agreement on a text for a full floor vote and will meet again on Tuesday afternoon.

Erdogan in July lifted his objections to Sweden's NATO membership after Stockholm cracked down on Kurdish groups that Ankara calls terrorists.

"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 Erdogan's ruling AKP party and head of the 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 Erdogan's ruling alliance holds the majority of seats.

NATO allies have piled pressure on Turkey, with France saying the credibility of the alliance was "at stake".

- Process fraught with problems -

But the process is fraught with problems.

In December, Erdogan suggested that parliament will only act on Sweden if the US Congress approves Turkey'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)," Erdogan said.

"All of these are linked," he added.

"Sweden's NATO membership and F-16 sales to Turkey will be handled in coordination to some extent... because unfortunately, neither country trusts the other," Ozgur Unluhisarcikli, the Ankara office director of the US German Marshall Fund think tank, told AFP.

Turkey's ageing air force has suffered from Ankara's expulsion from the US-led F-35 joint strike fighter programme in 2019.

This was in retaliation for Erdogan's decision to acquire an advanced Russian missile defence system that NATO views as an operational security threat.

US President Joe Biden's administration has repeatedly promised to move forward with the $20-billion F-16 sale but lawmakers have blocked it over concerns about Turkey's alleged violations of human rights and its past tensions with Greece.

"There is no strong consensus in the parliament on Sweden's NATO membership, nor in the US Congress on the sale of F-16s to Turkey," Unluhisarcikli said.

Erdogan's anti-Israel rhetoric after the start of its war with Hamas had raised concerns in Washington.

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

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