Political leaders in the NATO-aligned Baltic states are warning Finland and Sweden that a future path into the Western alliance may not be as automatic as they might assume and could take time to accomplish.

Estonian President Toomas Hendrik Ilves has advised nonaligned neighbor Finland to carefully consider the possible risks and implications that could attach to any future decision to apply for NATO membership.

Finland's path to NATO may be "winding" and problematic if the country were to apply for membership in the alliance while facing a security crisis and in need of external military support, Ilves said.

"In such a possible event, Finland might not necessarily secure support among all members of NATO. Then, the accession treaty would need to be accepted by the parliament of each member state. Many may possibly think the timing is bad," Ilves said.

Estonia, which meets the alliance's 2 percent of GDP military spending requirement, would face an identical situation to Finland or Sweden if it decided to join NATO today, Ilves said. Estonia joined NATO, along with Baltic neighbors Latvia sand Lithuania, in 2004.

"I can guarantee there will be countries saying, 'It's too provocative, this is not the time, we should wait. We do not want to scare Russia.' It's not automatic; a country just doesn't step in to NATO," Ilves said.

The long-term defense and security policies being pursued by Finland and Sweden are expected to be discussed when US President Barrack Obama hosts a summit meeting with Nordic political leaders in Washington on May 13.

Despite strong political support for NATO in Finland and Sweden, and with both states continuing to strengthen military collaboration, neither country has so far adopted a concrete position to join the alliance.

In order to pursue NATO membership, both Finland and Sweden are likely to run referendums, separately or jointly, to determine the level of public support before radically changing their military alliance-neutral positions.

Finland and Sweden signed a host nation support agreement (HNSA) with NATO in 2014. This provides for limited assistance from alliance forces in certain emergency situations.

The HNSA expands cooperation beyond the Partnership for Peace (PfP) arrangement reached between NATO and the two unaligned Nordic states in 1994. Under the HNSA agreement Finland and Sweden can "invite" NATO forces and weaponry onto their territories in a time of crisis.

The nonbinding agreement falls short of NATO's Article 5 collective defense provisions.

A number of Finland's political parties, including the National Coalition Party (NCP) and Swedish People's Party, support NATO membership.

Alexander Stubb, the NCP's party leader, believes that Finland needs to do more to reinforce its "geo-political identity" globally in order to underline that the country is "firmly in the Western sphere" and not closely aligned to Russia.

"Although Finland has a functional and practical relationship with Russia, its position as part of the West must not be called into question. We've been firmly part of the West for quite some time," Stubb said.

Finland, Stubb said, continues to actively build stronger transatlantic political partnerships and military relationships.

The ongoing public and political debates over possible NATO membership in Finland and Sweden have become more heated, even if neither country looks likely to join the alliance anytime soon, said Jannicke Fiskvik, an Oslo-based political and security analyst.

"Both governments have commissioned reports on the potential implications of a NATO membership; even though they currently seem unwilling to risk a reaction from Moscow by joining the alliance. In this regard, events in one of the Baltic States are more likely to serve as a game-changer," Fiskvik said.

The fear that Finland, which has an 820-mile border with Russia, could conceivably join NATO in the future, remains a constant cause of concern in Moscow.

In March, the Moscow-based Institute for Strategic Studies speculated that Finland and Sweden are likely to organize referendums on NATO membership in 2018.