STOCKHOLM (Reuters) - NATO will increase it's presence around Sweden's borders and in the Baltic sea while a potential application to join the alliance is processed, NATO Secretary-General Jens Stoltenberg told Swedish public broadcaster SVT.

       Sweden and neighbouring Finland have remained outside the alliance but Russia's annexation of Crimea in 2014 and its invasion of Ukraine have led the countries to rethink their security policies, with NATO membership looking increasingly likely.

       Both countries are seeking military protection assurances during an application process, which could take up to a year to be approved by all NATO's members.

       "I am convinced that we will find solutions for the security needs Sweden will have in a transitional period," Stoltenberg told SVT.

       "From the potential moment Sweden is applying, and NATO says that they want Sweden to join, there is a very strong obligation from NATO to be able to guarantee Sweden's security," Stoltenberg said, and added that it would include increased presence around Sweden and in the Baltic sea.

       Moscow has warned Sweden and Finland of "serious consequences" and that it could deploy nuclear weapons and hypersonic missiles in the European exclave of Kaliningrad if Sweden and Finland become NATO members.

       On Wednesday, Sweden's Foreign Minister Ann Linde said the U.S. had given Sweden "security assurances" for the application period, but "not concrete security guarantees."

       Sweden and Finland are expected to make a decision about whether to apply to join NATO this month.

       (Reporting by Johan Ahlander; Editing by Alexandra Hudson)