Sweden's bid to join NATO got a major boost when the Turkish parliament finally ratified its membership application this week. Yet with the Turkish president's signature still needed, Sweden's wait to join the military alliance may not be over.

After ten long months, the Turkish parliament on Tuesday evening overwhelmingly voted to approve Sweden's Nato membership.

Turkish President Recep Tayyip Erdogan has been holding up the ratification with a long list of demands from his allies, and the vote came after intensive diplomatic lobbying led by Washington. 

At the heart of the delay was Ankara's demand that the US Congress approve the sale of American F-16 fighter jets to replace Turkey's ageing airforce.

"Neither the United States nor Turkey trust each other on any level," said Asli Aydintasbas, an analyst with Washington-based think tank the Brookings Institution.

"There is also no trust here in Washington vis-a-vis the actions of the Turkish government," she continued. "They don't want to find themselves in a situation where they deliver on their end and the other side doesn't."

Mutual mistrust

That distrust was exacerbated by the apparent lack of personal chemistry between Erdogan and US President Joe Biden, who in the past has described the Turkish leader as a bully.

But the impasse was broken by a rare phone call between the two leaders last month. Biden reportedly convinced Erdogan that he could only persuade Congress to allow the jet sale to Turkey if the Turkish parliament ratified Sweden's NATO membership – a deal that goes back to last year, according to Sinan Ulgen of Edam, an Istanbul-based think tank.

"There is an agreement that was essentially struck during the last NATO summit in Vilnius whereby the US side would essentially start the formal notification of the F-16 package once the Turkish parliament ratifies the accession of Sweden to NATO," Ulgen said.

But behind Turkey's lengthy delay lies scepticism in Ankara whether Biden can deliver Congress.

Lame duck?

Hostility towards Erdogan over his authoritarianism and threats to neighbours, including Greece, is a rare issue that bridges the deep divide between US Democrats and Republicans.

Erdogan's strong backing of Hamas, which he calls a "liberation movement", has only added to that hostility.

Meanwhile, Biden is increasingly seen as a lame-duck president as 2024 elections approach.

"Now [Donald] Trump is marching on the way to triumph once more, maybe, probably. Biden cannot be exerting pressure over the Senate and House of Representatives for the sake of Turkey," predicts Sezin Oney, a commentator with Turkish news portal Duvar.

Oney points out Biden's failure to get Congress to sign off on funding for Ukraine can only add to Ankara's unease.

"I mean, he couldn't do it in the case of Ukraine; he's struggling with that. So how can he do it on behalf of Turkey, which doesn't deliver anything and, on top of it, supports Hamas?" she questioned.

• Turkey under fire after declaring Hamas a 'liberation' group
• Erdogan weighs benefits of friendlier ties with Turkey's Western allies

From Turkey to Hungary

Such concerns could yet further delay Sweden's membership.

While the Turkish parliament ratified NATO's expansion, Erdogan has to sign off on the legislation and send the document to the US State Department as per the military alliance's rules.

But political momentum is behind the deal.

"Congressional approvals really rely on key party spokespeople on the committees," said analyst Aydintasbas. "There is still overwhelming approval for the deal – enough numbers to make it past foreign relations committees in both houses, because it is so important for transatlantic unity, not because the US Congress approves of Turkey's foreign policy direction."

But even if the hurdle of Turkey is finally overcome, Hungary is yet to ratify – and Prime Minister Viktor Orban, after 20 months, is now demanding unspecified concessions from Sweden.

With Erdogan a close ally of Orban, NATO may yet need Turkey's assistance in finally bringing Sweden into the fold.