Turkey expects the NATO summit in Madrid will "reiterate and reinforce solidarity, unity and cohesion among allies," Foreign Minister Mevlüt Çavuşoğlu said on Tuesday.

"NATO's strong commitment to fight against terrorism in all its forms and manifestations is essential," said Çavuşoğlu in a video message shared by the Antalya Diplomacy Forum's social media account.

Çavuşoğlu said the Madrid summit is taking place at a "crucial time," and the war in Ukraine has "global implications" and poses a challenge for trans-Atlantic security.

"Our leaders will endorse the new strategic concept. This will shape our alliance's vision for the next decade. While NATO keeps adapting to the ever-shifting security environment, our core principle remains unchanged; One for all, all for one, as stated by Article Five of the Washington Treaty," he added.

Turkey's top diplomat went on to stress that NATO's commitment to the fight against terrorism is also "valid for the applicant countries."

"All must respect the principles of solidarity and each other's security concerns. There can be no ifs or buts about it. I believe NATO will continue to grow stronger in the years ahead," he said.

Sweden, along with Finland, formally applied to join NATO last month, a decision spurred by Russia's war on Ukraine, which began on Feb. 24.

But Turkey, a longstanding member of the alliance, has voiced objections to the membership bids, criticizing the countries for tolerating and even supporting terrorist groups.

NATO hopefuls Finland and Sweden voiced optimism on Tuesday that Turkey might lift its veto over their stalled bid to join the military alliance at a summit in Madrid, where U.S. President Joe Biden is set to meet President Recep Tayyip Erdoğan.

The White House confirmed Biden will meet Erdoğan during the summit that starts later on Tuesday and runs until Thursday, while two NATO diplomats said they expected Washington to seek to break the impasse.

Turkey's unexpected objections to the two Nordic countries' membership bid, which if successful would be the biggest shift in European security in decades, threatens to overshadow a summit striving for unity as Russia wages war in Ukraine.

"The general view is that the discussions went somewhat better, which should mean that understanding has somewhat increased on both sides," Finnish President Sauli Niinisto told reporters in Helsinki, referring to talks between diplomats.

Swedish Foreign Minister Ann Linde went further, telling daily Svenska Dagbladet (SvD): "We are prepared for the eventuality that something positive could happen today, but it might also take longer."

Erdoğan is set to meet NATO Secretary-General Jens Stoltenberg, Swedish Premier Magdalena Andersson and Niinisto at around 2 p.m. GMT in Madrid.

"We hope to make progress," Stoltenberg said.

Ankara's main demands are for the Nordic countries to stop supporting terrorist groups present on their territory, and to lift their bans on some sales of arms to Turkey.

Those conditions are now the subject of intense diplomacy as NATO allies try to seal the accession in record time as a way of solidifying their response to Russia, particularly in the Baltic Sea, where Finnish and Swedish membership would give the alliance military superiority.

In the wider Nordic region, Norway, Denmark and the three Baltic states are already NATO members. Russia's Feb. 24 invasion of Ukraine, which Moscow says is a "special operation," helped overturn decades of opposition to NATO membership in Sweden.

Before leaving for Madrid, Erdoğan in Ankara held firm on his stance, saying Turkey wanted action, not words, to address its concerns, adding he will also push Biden on an F-16 fighter jet purchase.

"We want results. We are sick of passing the ball around in the mid-field. As of now, they are producing words," Erdoğan said at the airport.

Erdoğan said he had spoken to Biden on Tuesday morning ahead of the planned Madrid meeting and would explain Turkey's position to allies at the summit and in bilateral meetings.

He said he would discuss with Biden the issue of Ankara's procurement of S-400 air defense systems from Russia – which lead to U.S. sanctions – and a request to buy 40 F-16 jets and modernization kits from Washington, as well as other bilateral issues.

Other allies, including France and Spain, indirectly urged Turkey to yield. Speaking at the G-7 summit in Germany, French President Emmanuel Macron called for a message of "unity and of force" from NATO in Madrid.

Spanish Prime Minister Pedro Sanchez, standing alongside Stoltenberg, said that there was no option but to let in Finland, which shares a 1,300-kilometer (810-mile) border with Russia, and Sweden.

"We are convinced that, if not now, it will be later, but eventually they will join the Atlantic alliance," Sanchez told reporters.