Turkey’s President Recep Tayyip Erdogan on Saturday said Ankara would not look “positively” on Sweden and Finland’s NATO bids unless its concerns were addressed, despite broad support from other allies, including the United States.

Turkey has long accused Nordic countries, in particular Sweden which has a strong Turkish immigrant community, of harbouring outlawed Kurdish rebels as well as supporters of Fethullah Gulen, the US-based preacher wanted over the failed 2016 coup.

Erdogan’s opposition has thrown a major potential obstacle in the way of the likely membership bids from the hitherto militarily non-aligned Nordic nations since a consensus is required in NATO decisions.

“Unless Sweden and Finland clearly show that they will stand in solidarity with Turkey on fundamental issues, especially in the fight against terrorism, we will not approach these countries’ NATO membership positively,” Erdogan told NATO chief Jens Stoltenberg in a phone call, according to the presidency.

On Twitter, Stoltenberg said he spoke with Erdogan “of our valued ally” on the importance of “NATO’s Open Door”.

“We agree that the security concerns of all Allies must be taken into account and talks need to continue to find a solution,” he said.

On Thursday, Stoltenberg said Turkey’s “concerns” were being addressed to find “an agreement on how to move forward”.

Erdogan speaks to leaders of Sweden and Finland

Erdogan, who refused to host delegations from Sweden and Finland in Turkey, held separate phone calls with the two countries’ leaders – Finnish President Sauli Niinisto and Swedish Prime Minister Magdalena Andersson – on Saturday, urging them to abandon financial and political support for “terrorist” groups threatening his country’s national security.

Erdogan called upon Sweden to lift defensive weapons export restrictions it imposed on Turkey over Turkey’s 2019 incursion into northern Syria, a Turkish presidential statement said.

The Turkish leader also said he expected Stockholm to take “concrete and serious steps” against the Kurdish Workers’ Party, or PKK, and other groups which Ankara views as “terrorists”.

Andersson tweeted that Sweden looked “forward to strengthening our bilateral relations, including on peace, security, and the fight against terrorism”.

The PKK has waged a rebellion against the Turkish state since 1984 and is blacklisted as a “terrorist organisation” by Turkey and Western allies like the European Union – which includes Finland and Sweden.

Erdogan told Finish President Sauli Niinisto “that an understanding that ignores terrorist organisations that pose a threat to an ally within NATO is incompatible with the spirit of friendship and alliance”, the statement added.

In return, Niinisto praised “an open and direct phone call” with Erdogan.

“I stated that as NATO allies Finland and Turkey will commit to each other’s security and our relationship will thus grow stronger,” he tweeted.

“Finland condemns terrorism in all its forms and manifestations. Close dialogue continues.”

Sweden and Finland, while solidly Western, have historically kept a distance from NATO as part of longstanding policies aimed at avoiding angering Russia.

But the two nations moved ahead with their membership bid in shock over their giant neighbour’s invasion of Ukraine, which had unsuccessfully sought to join NATO.

On Thursday, Niinisto and Andersson visited Washington, where they spoke with US President Joe Biden about their bids to join NATO in response to Russia’s invasion of Ukraine.

Biden said “Finland and Sweden make NATO stronger”, and offered the “full, total, complete backing of the United States of America”.