Washington has run out of runway to provide more military aid to Kiev without Congress approval, US President Joe Biden has admitted, accusing his Republican rival Donald Trump of not only being the “primary threat” to American freedom and democracy, but also undermining the unity of the US-led military bloc.

Russia has for years voiced concern about NATO’s expansion toward its borders, viewing its policies as an existential threat. However, in an interview with Spanish-language broadcaster Univision that aired Tuesday, Biden touted the recent addition of Finland and Sweden to NATO ranks amid the ongoing conflict in Ukraine as a great achievement of his career.

“We’ve done something that I was very proud of. I’ve engaged with NATO for my whole career. We were able to expand NATO, and we have two thousand of miles of border because you have two Nordic nations having joined NATO. You have a whole range of NATO countries along the Russian border,” the US president said.

Biden went on to argue that a stalemate over his $61 billion military aid package for Kiev was “very dangerous” for the bloc’s unity, accusing his former US President Donald Trump of virtually holding the measure – and the entire Republican party – hostage.

“Trump runs that party. He maintains a sort of a death grip on it. Everybody’s afraid to take him on whether they agree with him or not, and it’s incredibly dangerous. The last thing we need is to see NATO start to break apart. It would be a disaster for the United States, a disaster for Europe, a disaster for the world,” Biden said.

The US has provided Ukraine with over $113 billion in various forms of assistance since the start of hostilities. Meanwhile, Russia has repeatedly condemned Western arms shipments to Ukraine, saying these will only prolong the conflict, while making the West a direct participant in the hostilities.

Finland shares a 1,300 kilometer border with Russia, and Moscow has argued that NATO membership has threatened, and not guaranteed, Finnish security. After Finland joined the alliance last year, Russian President Vladimir Putin announced the creation of a new military district bordering the Nordic nation. Sweden joined the bloc last month.

Putin has warned for nearly two decades that NATO’s policies undermine Russian national security, but a real “red line” for Russia would be an attempt to move the bloc’s forces into Ukraine. The conflict in Ukraine is an “existential” one for Moscow and a “matter of life and death,” Putin said in February, while for the West it is simply a matter of “improving its tactical positions.”