Turkey's President Recep Tayyip Erdogan on Monday announced a new condition for approving Sweden's membership in NATO. He called on European countries to open the way for Turkey to join the European Union.

This came as a surprise announcement before departing to a NATO summit in Lithuania's capital, creating new uncertainty around Sweden's bid to become the alliance's 32nd member. Erdogan linked Turkey's ambition to join the EU with Sweden's efforts to become a NATO member, saying "Turkey has been waiting at the door of the European Union for over 50 years now, and almost all of the NATO member countries are now members of the European Union."

Glad to announce that after the meeting I hosted with @RTErdogan & @SwedishPM, President Erdogan has agreed to forward #Sweden's accession protocol to the Grand National Assembly ASAP & ensure ratification. This is an historic step which makes all #NATO Allies stronger & safer. pic.twitter.com/D7OeR5Vgba

— Jens Stoltenberg (@jensstoltenberg) July 10, 2023

He added, "Come and open the way for Turkey's membership in the European Union. When you pave the way for Turkey, we'll pave the way for Sweden as we did for Finland." NATO Secretary-General Jens Stoltenberg said he supports Turkey's ambition to join the EU but noted that it wasn't among the conditions listed in an agreement that Sweden, Finland and Turkey signed at last year's NATO summit in Madrid.

Stoltenberg reiterated that Sweden had met those conditions and said he thinks it is "still possible to have a positive decision" on the country's pending membership during this week's summit in Lithuania. The White House readout of Biden and Erdogan's call did not mention the issue of Turkish membership in the EU.

However, the U.S. President's national security adviser Jake Sullivan confirmed they had spoken about Sweden's NATO membership and had agreed to meet in Vilnius for further talks. He said the White House is confident Sweden will join the alliance "if it happens after Vilnius — we're confident it will happen." Erdogan's latest comments stunned seasoned Turkey analysts.

Paul Levin, director of the Institute for Turkish Studies at Stockholm University, said, "Erdogan has introduced new demands and moved the target repeatedly throughout this process, but trying to put pressure on the EU over a NATO matter is rather spectacular."

He added, "What can be said is that if he were to actually condition Swedish NATO accession on a reboot of the Turkish EU accession process, then Sweden is unlikely to become a NATO ally anytime soon." Before Erdogan's comments, Swedish Foreign Minister Tobias Billström had expressed optimism that Turkey would drop its objections to Stockholm's NATO bid. Billström insisted Sweden had fulfilled its part of the deal with Finland and Turkey, which included lifting arms embargoes on Turkey, tightening anti-terror laws and stepping up efforts to prevent the activities of the outlawed Kurdistan Workers' Party, or PKK.

Erdogan on Monday repeated that Turkey expected Sweden to fulfill its pledge to crackdown on groups that Ankara considers to be terrorists. He said, "We are tired of repeatedly saying that (Sweden) needs to fight terrorist organizations and their extensions indiscriminately."

It remains to be seen how the NATO summit will progress and whether Erdogan's condition will be accepted. However, it is clear that Turkey's EU ambitions are now linked to Sweden's bid to become a NATO member.