In a Facebook post, Sakaliene said she and Prime Minister Inga Ruginiene, who is from the same Social Democratic Party (LSDP), have "fundamentally different ideas on how to strengthen defence".

Ruginiene described the resignation as "inevitable", stressing that she could not accept that "misunderstandings and problems arise in an area as important as defence".

Lithuania, which borders Belarus and the Russian enclave of Kaliningrad, boosted its military following Russia's 2022 invasion of Ukraine, fearing it could possibly be Moscow's next target.

The dispute erupted after the minister and prime minister attended a meeting last week with defence analysts, after which some participants said they no longer expected the government to keep its promise to spend five percent of GDP on defence.

On October 15, Ruginiene announced that the draft state budget for 2026 does include 4.8 billion euros ($5.6 billion) in defence, or 5.4 percent of GDP, making Lithuania one of NATO's top spenders.

On Wednesday, the prime minister, quoted by the Baltic news agency BNS, expressed her determination to work to ensure that the defence budget "continues to increase".

She also accused Sakaliene of showing a "total lack of will" to cooperate.

Lithuania is governed by a coalition of parties, primarily the LSDP and the populist Dawn of Nemunas party.

At a summit in June in The Hague, NATO set a new target for its 32 member countries to devote five percent of GDP to defence by 2035.

In 2024, more than a quarter of NATO countries remained below the two percent target that had been the previous objective, according to the alliance's latest estimates.