As host of last week's summit of the alliance's leaders, Spain, like other members, committed to increasing its investment in defence to 2.0 percent of its gross domestic product (GDP), as required by NATO.

Without waiting for the next round of tortuous budget negotiations, Sanchez's cabinet on Tuesday released 999.7 million euros ($1.02 billion) in military funding to "deal with all the extraordinary expenses" linked to the war in Ukraine, government spokesman Isabel Rodriguez said.

The funding was released as part of the "commitment" Sanchez made to NATO, she said.

According to NATO's latest annual report, Spain invested 1.03 percent of its GDP on defence spending in 2021, one of the lowest figures among alliance members, with only Luxembourg investing less.

But Podemos, Sanchez's junior coalition partner which has been highly critical of arms shipments to Ukraine, roundly rejected the military funding injection and opposes raising the defence budget.

Labour Minister Yolanda Diaz, who represents the party in government, on Tuesday called for an "urgent" meeting of the coalition's monitoring committee which is tasked with ensuring that the commitments made when the coalition deal was inked in January 2020 were being respected.

Podemos said it had only heard about the allocation of funds to the military through the press -- a charge denied by the Socialist party.

"Spending on weapons at the demand of a foreign power rather than investing it in better healthcare, education and social protection is not a budget that our country needs," said Podemos' leader and Social Rights Minister Ione Belarra said on Monday.

In an interview with the local daily El Diario Montanes, Foreign Minister Jose Manuel Albares, who belongs to the Socialist Party, said he could not comprehend Podemos' opposition.

"I can't believe that any political force could be against guaranteeing Spain's security and protection at a time when the threat to our security has increased in a way that it hasn't done in decades," he said.