• Erdogan on Monday once again threatened to derail Finland and Sweden's NATO ambitions. 
• Turkey has accused the Nordic countries of being too friendly with Kurdish groups it considers to be terrorists. 
• Erdogan's warning came a day before he met with Putin in Iran.

Turkish President Recep Tayyip Erdogan on Monday once again threatened to stand in the way of Finland and Sweden joining NATO — a day before he met with Russian President Vladimir Putin in Iran.

"I would like to remind once again that if these countries do not take the necessary steps to fulfill our conditions, we will freeze the (accession) process," Erdogan said in a televised addressed, per the Associated Press. "Our stance on this issue is very clear. The rest is up to them."

Turkey has accused the Nordic countries of being too friendly with Kurdish militant groups it considers to be terrorists, while also taking issue with embargoes on arms exports. Along these lines, Turkey initially said it would block Finland and Sweden from joining the alliance. NATO enlargement requires unanimous agreement from all current members. But Turkey dropped its objections last month after coming to an agreement with Finland and Sweden.