STOCKHOLM, May 16 (Reuters) - Sweden will formally apply for NATO membership in the next few days, Prime Minister Magdalena Andersson said on Monday, but its accession process, and that of Finland, hit a snag when NATO member Turkey's president said he would not approve either bid.

Sweden and Finland need each of NATO's 30 members to approve their applications. The ratification process had been expected to take up to a year, though Turkey's objections have thrown that into doubt.

At a news conference, Turkish President Tayyip Erdogan said Sweden and Finland should not bother sending delegations to Ankara to persuade Turkey to support for their bids.

"Neither of these countries have a clear, open attitude towards terrorist organisations," Erdogan said. "How can we trust them?"

He called Sweden a "hatchery" for terrorist organisations with terrorists in parliament. read more

Russia's invasion of Ukraine has shaken up Europe's security architecture and forced Sweden and Finland to choose sides after staying out of the U.S.-led NATO alliance during the Cold War.

Sweden's Social Democrat government, worried the country will be vulnerable while its application is considered, had been hoping for a quick ratification process. read more

But Turkey's objections, which NATO leaders initially hoped would not cause a major delay, now look to present a serious obstacle.