Sweden's decision to join NATO (North Atlantic Treaty Organization) could come at significant cost, its Prime Minister has warned.

On Tuesday morning, the country finally signed its bid to join the world's largest military alliance — a day after Magdalena Andersson announced the historic decision with the backing of Swedish parliament.

In doing so, she stressed that her country's policy of neutrality in armed conflicts has served it well over the past two centuries, but that the regional security threat has changed considerably since the start of the conflict in Ukraine.

"[It is] is an attack on European security and has thrown Sweden into a new and dangerous reality. Unfortunately, we don't believe Russia will change course in the foreseeable future," she said during a press conference.

READ MORE

What is NATO and why is Russia worried?

Boxing away stress in Kyiv

What can Finland's military offer NATO?

Andersson also warned its accession to NATO could make Sweden particularly vulnerable to cyberattacks as well as the spread of misinformation. She called on all Swedes, and perhaps fellow politicians, to show unity by not giving into division ahead of this fall's general election.

The formal decision to join NATO follows the release of a government security assessment last week. In this report, a majority of Sweden's parties agreed that the country joining NATO alongside Finland would have a deterrent effect against possible Russian activities in Northern Europe. It also concluded that membership would enhance security in the Baltic Sea and across NATO as a whole.

But not all local politicians have welcomed the decision with open arms. Nooshi Dadgostar, leader of the Left Party, opposes NATO membership and has criticised the government for rushing its decision to join the block. She has even called it undemocratic, an opinion that was also echoed by some members of the public that CGTN spoke to.

But while the majority of countries in the military alliance appear to favour joining NATO, the biggest challenge to membership could come from one of its existing member states. Turkey has indicated it could veto the move, which took NATO allies by surprise last week.

While Swedish and Finnish officials had planned to travel to Ankara to address these objections, Turkish President Tayyip Erdogan has told them not to bother coming.

The leader said during a news conference (on Monday) the countries can't be trusted over their ties to groups Ankara regards as terrorist organisations.

Turkey has accused Sweden and Finland of having links to militant organization Kurdistan Workers Party (PKK) as well as followers of Fethullah Gulen, whom it believes was behind a coup attempt in 2016.