Both Finland, which has one of Europe's longest borders with Russia, and Sweden dropped their decades-long policies of military non-alignment and applied to join the alliance last May in the wake of Moscow's invasion of Ukraine.

But facing fewer diplomatic hurdles than Stockholm, Helsinki wants to move forward even before Finland's general elections in April, as public opinion also supports membership.

After debates on Tuesday, a vote is scheduled by Finnish MPs on Wednesday afternoon for speeding up the ascension process, as the two countries have the backing of all but two of NATO's 30 members, the holdouts being Hungary and Turkey.

Many Finnish lawmakers have pushed for legislation affirming that Finland accepts the terms of the NATO treaty even before elections on April 2.

Only a handful of MPs voiced opposition during the debate on Tuesday.

Markus Mustajarvi from the Left Alliance party -- which has been vocal in its NATO opposition in the past -- asked the parliament to strike down the bill, triggering a vote for Wednesday.

Mustajarvi's criticism focused on the lack of guarantees that nuclear weapons would not be placed in Finland.

"Finland must act in such a way that its actions ease, not increase, tensions between nuclear powers," said Johannes Yrttiaho, another Left Alliance MP.

But Foreign Minister Pekka Haavisto told MPs that "this decision and legislation will not change Finland's position on nuclear weapons".

Having the bill passed means that Finland can act swiftly even if the ratifications come in before a new government has been formed.

"The time is now to ratify and to fully welcome Finland and Sweden as members," NATO chief Jens Stoltenberg said Tuesday during a visit to Finland.

On Tuesday, Finland also announced the start of construction of its planned 200-kilometre fence on the Russian border.

- Talks with Turkey -

The legislation is expected to pass easily, after the initial membership bid in May was supported by 188 of the 200 members in parliament.

Yet Turkey is blocking the bids, accusing Sweden in particular of providing a haven for what it considers "terrorists", in particular members of the Kurdistan Workers' Party (PKK).

Sweden's Prime Minister Ulf Kristersson has said Finland's joining alone could "complicate" the close military cooperation between the Nordic countries, since Sweden would remain alone outside of NATO protection.

But on Monday, Turkish Foreign Minister Mevlut Cavusoglu said that Ankara now looked favourably on Finland's bid, adding that "We may separate Sweden and Finland's membership process".

While passing the bill does not mean that Finland will automatically join NATO after ratification by Turkey and Hungary, it puts in place a deadline for how long it can wait for its neighbour.

The government's chancellor of justice, Tuomas Poysti, said that after the bill is approved by the parliament, the president can wait a maximum of three months to sign it.

Finland's President Sauli Niinisto told reporters last week that he intended to sign the law "as soon as it is approved by Parliament" but "if there are practical reasons, I can wait".

"But not beyond the elections" set for April, he added.

Cavusoglu also announced Monday that negotiations between Turkey, Finland and Sweden would resume on March 9, after talks with Sweden were dropped over a row about protests held in Stockholm, including a burning of the Koran in front of Turkey's embassy.