For months, Nato leaders had hoped that when they convened for their annual summit next week, they could use the occasion to welcome Sweden as the alliance’s newest member.

Now, that outcome appears all but impossible, as stalling by Hungary and continued objections by President Recep Tayyip Erdogan of Turkey have drawn out the process, raising questions about when Sweden might be able to join and what sort of breakthrough would be necessary.

All 31 member states must agree to admit new members, and the split over Sweden risks denting the alliance’s ability to project a united front against President Vladimir V. Putin of Russia as his forces seek to beat back a Ukrainian counteroffensive.

Nato officials say the hope is to get all the alliance’s leaders to agree at the two-day summit set to begin on Tuesday in Vilnius, the Lithuanian capital, to let Sweden join. Then, the thinking goes, Erdogan and Prime Minister Viktor Orban of Hungary can push the approval through their respective parliaments.

To that end, Jens Stoltenberg, the Nato secretary general, will meet senior foreign, defence and intelligence officials from Turkey, Sweden and Finland in Brussels on Thursday, in an effort to convince the Turks that Sweden, like Finland, has done enough to overcome Turkish objections.

On Tuesday, foreign minister Peter Szijjarto of Hungary told reporters that he was in touch with his Turkish counterpart and that if Ankara’s position changed, Hungary would not obstruct the process. That leaves the ball in Erdogan’s court.

New York Times News Service