Swedish Prime Minister Magdalena Andersson, seeking to win Turkish support for her country's bid to join NATO, pledged on Monday not to let Sweden become "a safe haven for terrorists."

Turkey has blocked bids by Sweden and Finland to join the Western military alliance, accusing them of harboring Ankara's foes, including members of the banned PKK terrorist group and its branches.

The two historically neutral Nordic countries applied to join NATO last month, one of the biggest shakeups in European security for decades, in response to Russia's invasion of Ukraine.

"Our stance regarding the PKK is crystal clear. It is listed as a terror organization in the European Union, and is regarded as such by Sweden," Andersson told reporters in Brussels after meeting NATO Secretary-General Jens Stoltenberg ahead of an alliance summit in Spain this week.

"Sweden is not and will not be a safe haven for terrorists. The relevant authorities work intensively in order to expel persons who could be a security threat – and there are a substantial number of cases which are currently processed," Andersson said.

"Sweden condemns terrorism in the strongest possible terms. We are unequivocally committed to the fight against terrorists in all its forms and manifestations," she added.

Swedish, Finnish and Turkish officials met in Brussels on Monday, Sweden's premier said, voicing "strong hope that dialogue can be successfully concluded in near future."

"Sweden will contribute to the security of NATO as a whole, including Turkey, in the spirit of solidarity," she said.

Andersson said she spoke to the Turkish president on Saturday and the talk was "good and constructive."

Continuing on Sweden's efforts in the fight against terrorism, the prime minister said "constitutional amendments are being prepared, which would pave the way for criminalization of participation in terrorist organizations."

"There should be no doubt that Sweden will continue to stand firm alongside other like-minded countries in the fight against terrorists," she added.

Turkey's requests for extradition of terrorists are "handled swiftly and carefully" by the Swedish legal system, in accordance with the European convention on extradition, Andersson said.

Turkey's security concerns on Nordic membership bids are legitimate and must be addressed, NATO Secretary-General Jens Stoltenberg also said on Monday.

Speaking at the joint press conference with Andersson, ahead of the NATO summit in Madrid, Stoltenberg said, "No ally has suffered more at the hands of terrorists ... including grievous attacks by the terrorist group PKK."

The NATO chief said the alliance should redouble its efforts in the fight against terrorism, and a special session devoted to NATO's counterterrorism efforts will be convened during the summit in the Spanish capital.

"We are now working together on an agreement between Sweden, Finland, and our ally Turkey to further address security concerns, including around arms exports and the fight against terrorism," Stoltenberg said.

He said President Recep Tayyip Erdoğan, Finnish President Sauli Niinisto and Swedish Prime Minister Magdalena Andersson have agreed to meet on Tuesday at the summit.

"That will be a further opportunity to address Turkey's concerns and move forward with NATO accession for Finland and Sweden," he added.

Finnish and Swedish leaders will discuss their stalled NATO bids with Erdoğan on Tuesday in a push to convince him at the start of a summit in Madrid.

But Ankara said the four-way meeting, which will also involve Stoltenberg, did not mean it was close to lifting objections to the two Nordic countries joining the military bloc.

Officials said Monday the leaders will meet in Madrid, in a last-ditch bid to break to the deadlock that threatens to overshadow the NATO summit, which will focus on Russia's invasion of Ukraine.

Representatives from Ankara, Helsinki and Stockholm held a fresh round of talks on Monday at NATO's headquarters in Brussels to try to hammer out the differences.

Russia's invasion of Ukraine earlier this year saw the two Nordic countries abandon decades of military non-alignment by applying in May for NATO membership. But the joint membership bid, initially believed to be a speedy process, has been delayed by objections from NATO member Turkey.

Ankara has accused Finland and Sweden of providing a safe haven for PKK terrorists whose decades-long insurgency against the Turkish state has claimed tens of thousands of lives. The Turkish leader has also called on Sweden and Finland to lift arms embargoes imposed against Turkey in 2019 over Ankara's military operation in Syria.

Erdoğan signaled over the weekend that no progress had been made in Sweden's bid to join NATO, urging Stockholm to take "concrete actions" to meet Ankara's concerns.

He said Monday after the Cabinet meeting that Turkey "will provide documents and images demonstrating our interlocutors' hypocrisy" toward groups Ankara views as terrorists.

Erdoğan also said he will do "whatever is necessary for our country’s rights and interests" at the NATO summit in Spain Tuesday.

"We will tell them clearly that it is not possible to expect a different attitude from Turkey unless this picture changes," he added.

Turkish officials said Ankara does not view the summit as a final deadline for resolving its objections.

Erdoğan's chief foreign policy adviser said Tuesday's four-way meeting did not mean that an agreement was imminent.

"Participating in this summit does not mean that we will step back from our position," Ibrahim Kalın said.

"We are conducting a negotiation. It has many stages."

Kalın said Finland and Sweden need to make "serious changes" to their laws "and constitution" – targeting terrorist groups.

"We want you to show the same change against the PKK and its affiliated YPG, PYD and similar structures," he said, referring to PKK-linked groups operating in Syria and Iraq.

Stoltenberg insisted that Sweden had "taken concrete steps in recent days to directly address Turkey's concerns."

"You have already amended Swedish law. You have launched new police investigations against the PKK and you are currently looking at Turkish extradition requests," he told Andersson.

"These concrete steps represent a paradigm shift in Sweden's approach to terrorism."

While the two Nordic countries said talks to resolve the dispute would continue, Erdoğan said recently that Ankara had not received any responses to its demands, including stopping support for terrorist groups, lifting arms embargoes on Ankara and extraditing terrorism suspects it seeks.

Earlier this month, Turkey has said documents it received from Sweden and NATO in response to the earlier written demands it presented the two candidates were far from meeting its expectations and any negotiations must first address Turkish concerns.

Ankara has previously said the Madrid summit is not a deadline. Any NATO membership requires the approval of all 30 members of the alliance. Turkey has been a NATO ally for more than 70 years and has the alliance's second-biggest army.