(Bloomberg) -- Sweden and Finland are starting to win assurances of help if threatened by Russia in the interim period between an expected application to join defense alliance NATO and an eventual entry under the bloc’s collective security umbrella.

The two Nordic countries, which began to seriously consider joining the North Atlantic Treaty Organization after Russia’s invasion of Ukraine, have worried of an insecure “gray period” on the doorstep of the bloc, before full membership unlocks its security guarantees.

The U.S. is “ready to provide various forms of security assurances” to both countries, Swedish Foreign Minister Ann Linde said on Wednesday after talks with Secretary of State Antony Blinken in Washington, D.C., according to public broadcaster SVT. Also on Wednesday U.K. Defense Secretary Ben Wallace told reporters in Finland that “it’s inconceivable that Britain would not come to the support of Finland or Sweden if it was ever attacked,” regardless of what stage of the NATO entry process they are at, according to multiple media.

The assurances from the U.S. are not the same as security guarantees, Linde said, but they would mean that “it would be clear to Russia that if they conduct any negative activities toward Sweden, which they have threatened, the U.S. would not let that pass unnoticed, without doing anything.”

The “best security guarantee” would be to “keep the ratification process as short as possible,” Finnish Prime Minister Sanna Marin told reporters in Copenhagen on Wednesday, referring to the 30 parliaments in NATO countries that have to sign off on any new members.

The worries are not unfounded, Swedish Premier Magdalena Andersson signaled. “Russia has been clear, they will respond to an application. We are aware of that,” she said.

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