Ibrahim Kalin, Mr Erdogan’s spokesman and chief foreign policy adviser, told Spain’s El Pais newspaper that the process would only “advance” once the Nordic countries had met Turkey’s demands.
Stockholm and Helsinki applied to join the Western defence alliance last month in response to Russia’s invasion of Ukraine, but they have faced opposition from Turkey, which has accused them of supporting and harbouring Kurdish militants and other groups it deems terrorists.
Mr Erdogan said on Wednesday that he had not received any concrete proposals on Turkey’s demands, which includes extraditing suspects sought by Turkey, and lifting arms embargoes on Ankara.
“It depends on what Sweden and Finland do,” Mr Kalin said. “When we see progress on our requests, then the process will advance. NATO is not a tourism, nor economic alliance; it is a security alliance, which means that it must provide security to all its members equally and fairly.”
During a visit to Washington this week, Nato secretary-general Jens Stoltenberg said that he would convene senior officials from Finland, Sweden and Turkey in Brussels in coming days to discuss the issue.
A bid to join Nato requires backing from each of its 30 members.
Turkey has said it will not change its position unless the countries take “concrete steps” to address its concerns.
While Finland and Sweden had initially hoped for a fast accession into Nato, the country is prepared for a longer and more complex process. Foreign minister Pekka Haavisto told the Svenska newspaper last month that talks were likely to continue for several weeks, with late June touted as a possible deadline.
Last week, Finland’s ambassador to the UK Jukka Siukosaari told the Standard that his country would take a “pragmatic approach” to dealing with Turkey’s concerns.
“The way we see it, we need to get to the bottom of things, understand what Turkey’s concerns are and see how we can meet them,” he said. “It’s a diplomatic process, and it’s better to do that behind closed doors than in the public eye.”