Progress on Finland and Sweden's applications for NATO membership ahead of the alliance's Madrid summit in June depends on their reaction to Turkey's demands, Turkish presidential spokesman Ibrahim Kalin said.

Stockholm and Helsinki had applied to join the Western defense alliance but faced opposition from Turkey, which accused them of supporting and harboring Kurdish fighters and other groups it considers terrorists.

While Sweden and Finland have said talks with Turkey will continue to resolve their differences, President Recep Erdogan said Wednesday that Ankara has not received any proposals for its demands.

Ibrahim Kalin said in an interview with El Pais that Finland's and Sweden's reactions to Turkey's demands will determine whether progress can be made ahead of the June 29-30 NATO summit in Madrid. "It depends on what Sweden and Finland do," he said. "When we see progress on our requests, then the process will move forward. NATO is not a tourist or economic alliance, it is a security alliance, and that means it must provide security to all of its members equally and fairly."

NATO Secretary-General Jens Stoltenberg said during a visit to Washington that he would convene senior officials from Finland, Sweden and Turkey in Brussels in the coming days to discuss the issue.

The application for NATO membership requires the support of each of its 30 members. Turkey, a NATO ally for more than 70 years, has said it will not change its position unless the Nordic countries take concrete steps to address its concerns.