Washington is using the potential sale of F-16 fighter jets as bait to force Ankara to ratify Sweden's and Finland's NATO membership applications, Bloomberg writes.

New tensions flared last week after protesters in Stockholm linked to Kurdish movements hung an effigy of President Recep Tayyip Erdogan, prompting Turkey to put more pressure on Sweden to crack down on banned groups.

Ahead of Turkey's June elections, Erdogan has repeatedly hinted that the vote could take place in May to throw the opposition off balance, and the situation seems more uncertain - even if NATO diplomats are confident that it will eventually be resolved, perhaps just in time for the alliance's Vilnius summit in July.

So far, 28 of NATO's 30 members have ratified the Nordic bids, while Turkey and Hungary have stayed away.

Sweden and Finland submitted their applications for membership in May following Russia's invasion of Ukraine. Turkey's opposition came as a surprise, since it had not previously objected.

The agreement reached at the NATO summit in Madrid in June made headway, but Ankara's position has changed little.

Turkey says Sweden must do more to combat support for terrorists among the Kurdish population of about 100,000, as well as to extradite suspects. 

Sweden must show with actions, not just words or statements, that the PKK will not be present, it will not be allowed to collect money or recruit members, presidential spokesman Ibrahim Kalin said earlier.

Following last week's protest, Turkey summoned the Swedish ambassador, opened an investigation and canceled a planned visit to Ankara by the speaker of the Swedish parliament. The Swedish government condemned the protests, calling them disgusting and an attempt to sabotage the NATO bid.

The Swedish government has tightened its anti-terrorism laws, but has acknowledged that it will not be able to meet all of Turkey's demands.

Although Sweden has deported at least one of the suspects wanted by Erdogan, its government cannot overturn a court decision in extradition cases where the judiciary has refused to send the accused to Ankara.

Erdogan's leverage

For Erdogan, the leverage he now has over Finland and Sweden is potentially a once-in-a-lifetime political gift after years of feeling that allies were oblivious to his concerns about terrorism.

He was very unhappy with a number of NATO countries, and I'm sure he wanted to advance his position in the broader NATO sphere by using Sweden and Finland to join, Finnish President Sauli Niinistö said of Erdogan in an interview with the Swedish publication Dagens Nyheter.

Making demands in the first place makes the 68-year-old Erdogan seem strong to voters as he seeks to extend his rule for another five years.

Erdogan will hold Finland and Sweden's membership hostage as long as he thinks it will benefit him, said Minna Alander, a researcher at the Finnish Institute of International Affairs. She said Turkey's leader is probably weighing whether it would be more advantageous for him to ratify the applications before or after the election.

NATO diplomats are cautiously optimistic that the issues will eventually be resolved, most likely after the Turkish elections. One noted that NATO's strengthening ultimately works to Turkey's advantage, especially in the Black Sea and the Middle East.

Alliance chief Jens Stoltenberg reiterated last week that he was confident that the accession of the Nordic countries would be ratified. He noted that for Finland and Sweden, the process, which could take years, has already progressed faster than for any other country in the alliance's modern history.

U.S. strategy

While it is not surprising that Erdogan is eager to use his leverage for as long as possible, there is one catch: the U.S., the most powerful country in the military alliance, has backed the Nordic countries with its authority. Washington is also using the potential sale of $20 billion worth of F-16 fighter jets as bait to get Ankara to comply.

The U.S. has warned Turkey that Congress may not approve the plane sale if Ankara does not ratify Sweden's and Finland's NATO bids, a senior Turkish official said on condition of anonymity. U.S. officials have linked the problems, , but the Biden administration has refrained from telling Ankara that receiving the planes will not happen until after the bids are ratified.

Now Erdoğan must decide whether and when to bow to Washington's pressure.