VILNIUS, Lithuania — Sweden’s membership of NATO took a big step forward on Monday after Turkey agreed to remove one of the last major roadblocks in return for help in reviving Turkey’s own chances of joining the European Union.

At talks in the Lithuanian capital Vilnius, where President Joe Biden and his NATO counterparts are meeting for a two-day summit starting Tuesday, Turkey’s President Recep Tayyip Erdogan committed to put the Nordic country’s accession protocol before Parliament “as soon as possible,” the head of NATO said.

“This is an historic day because we have a clear commitment by Turkey to submit the ratification documents to the Grand National Assembly, and to work also with the assembly to ensure ratification,” NATO Secretary-General Jens Stoltenberg told reporters after a series of high-stakes meetings.

Sweden’s NATO accession has been held up by objections from Turkey since last year. The Turkish parliament’s ratification of the accession protocol is one of the last steps in the process.

Stoltenberg made the announcement after talks with Erdogan and Swedish Prime Minister Ulf Kristersson on the eve of a NATO summit in Lithuania.

”Today we took a very big step on the road toward complete ratification,” Kristersson said.

There was no comment from Erdogan on the move, which many saw as linked in part to Turkey’s demands on other issues, particularly Erdogan’s desire for support for European Union membership from European leaders and for F-16 fighter jets from the United States.

Uncertain Timeline for Sweden’s NATO Membership

It’s unclear when the Nordic country’s membership might be approved, but the agreement appears to have taken the issue off the agenda of the summit, which was meant to focus uniquely on the war in Ukraine and Kyiv’s own membership aspirations.

In a statement, Biden welcomed the agreement and said he will work with Turkey “on enhancing defense and deterrence in the Euro-Atlantic area. I look forward to welcoming Prime Minister Kristersson and Sweden as our 32nd NATO Ally.”

Biden’s reference to enhancing Turkey’s defense capability was a nod to Biden’s commitment to help Turkey acquire new F-16s, according to a U.S. administration official, who spoke on condition of anonymity because he was not authorized to comment.

The Biden administration has backed Turkey’s desire to buy 40 new F-16s as well as modernization kits from the U.S. It’s a move some in Congress, most notably Senate Foreign Relations Committee Chairman Bob Menendez, D-N.J, have opposed over Turkey blocking NATO membership for Sweden, its human rights record, its relations with Greece and other concerns.

In Washington, however, Menendez said he was “continuing to have my reservations” on providing the planes to Turkey. If the Biden administration can show that Turkey wouldn’t use the F-16s belligerently against other NATO members, particularly its neighbor Greece, “then there may be a way forward,” Menendez told reporters.

Turkey’s EU Membership Discussions

In exchange for Turkey’s help with NATO, Sweden has agreed to help unblock Turkey’s progress towards joining the European Union, which has been on hold since 2018.

Stoltenberg said that Turkey’s relationship with the EU was “not an issue for NATO, it’s an issue for the European Union.” But he told reporters that “what Sweden agreed today as an EU member was to support actively the efforts to reinvigorate Turkey’s EU accession process.”

Earlier Monday, Erdogan had warned that he would block Sweden’s attempt to become the 32nd NATO ally unless European members of the military organization “pave the way” for Turkey to join the world’s biggest trading bloc.

It was the first time that he had linked the two countries’ aspirations in this way.

“Come and open the way for Turkey’s membership in the European Union,” Erdogan told reporters before flying to Vilnius. “When you pave the way for Turkey, we’ll pave the way for Sweden, as we did for Finland.”

Turkey was blocking Sweden’s accession because Erdogan believes that Sweden has been too soft on Kurdish militants and other groups that he considers to be security threats.

On arriving in Vilnius, Erdogan first met with Kristersson, before breaking off for separate talks with European Council President Charles Michel.

Michel tweeted that he and Erdogan had “explored opportunities ahead to bring cooperation back to the forefront and re-energise our relations.” Michel said he has tasked the European Commission to draw up a “report with a view to proceed in strategic and forward-looking manner.”

Turkey’s EU Accession Difficulties

Turkey first applied to join what is now the EU in 1987, but its membership talks have been at a standstill since 2018 due to democratic backsliding during Erdogan’s presidency, concerns about the rule of law and rights abuses, as well as disputes with EU-member Cyprus.

Of the 31 NATO member countries, 22 are also members of the EU, like Sweden.

Stoltenberg and Kristersson said that Sweden would also help Turkey to improve its customs arrangements with the EU, and to try to obtain visa-free travel in Europe for its citizens. Turkey tried to achieve these goals in recent years but failed to meet the trading bloc’s standards.

Earlier, Erdogan’s office said he told Biden during a telephone call Sunday that Turkey wanted a “clear and strong” message of support for Turkey’s EU ambitions from NATO leaders. The White House readout of the Biden-Erdogan call did not mention the issue of Turkish EU membership.

Sweden’s NATO Membership: A Matter of Timing

Turkey’s delaying tactics have irritated other NATO allies, including the United States. Biden’s national security adviser, Jake Sullivan, confirmed Sunday that Biden and Erdogan had discussed Sweden’s NATO membership, among other issues, and had agreed to meet in Vilnius for further talks.

Sullivan said the White House is confident Sweden will join the alliance.

“We don’t regard this as something that is fundamentally in doubt. This is a matter of timing. The sooner the better,” he said.

Previously non-aligned Sweden and Finland applied for NATO membership last year following Russia’s invasion of Ukraine. Finland joined in April following Turkish ratification.

Another key issue at the summit in Vilnius will be how to bring Ukraine closer to NATO without actually joining, and security guarantees Kyiv might need to ensure that Russia doesn’t invade again after the war ends. Ukrainian President Volodymyr Zelenskky will join the summit in person on Wednesday.

Stoltenberg said the most important thing was to continue to support Ukraine’s efforts to resist the Russian invasion.

“Unless Ukraine prevails, there is no membership issue to discuss at all,” he said.