President Joe Biden and 2024 candidate Donald Trump have criticized NATO as “dumb”, “disgraceful” and “un-American”.

The Democrat attacked Mr Trump for saying he would “encourage” Russia to attack any NATO member that fails to meet its defense spending quotas.

Mr Biden said the comments underlined the urgency of delivering a $95bn (£75bn) foreign aid package to US allies.

The bill passed the Senate, but it faces political headwinds in the House.

At the White House on Tuesday, Mr Biden said failure to pass a $60bn package for Ukraine would “play into Putin's hands”.

He said stocks had been boosted by Mr Trump's “dangerous” comments over the weekend.

“No other president in history has bowed to a Russian dictator,” Mr Biden said.

“Let me make this as clear as I can. I will never. For God's sake. It's dumb. It's shameful. It's dangerous. It's un-American.”

At a rally in South Carolina on Saturday, Mr Trump, a Republican, criticized the “false” payments by NATO members.

He described a past conversation he had with the leader of “a major country” about a possible attack by Russia.

Mr Trump said the official asked if the US would protect a NATO member that defaulted on its financial obligations.

“I said: 'You didn't pay? Are you guilty?'” Mr Trump told the crowd. “'No, I won't protect you, in fact I'll encourage them to do whatever they want. You have to pay.'

Mr Biden said his predecessor was treating the military alliance like a security scam.

“As long as I'm president, if Putin attacks a NATO ally, the United States will defend every inch of NATO,” he said.

Mr Biden noted that NATO invoked Article 5 only after the 11 September 2001 US attacks – as part of its charter which states that an attack on NATO member states requires collective defense by all.

In a message aimed at House Republicans, the president said: “Are you going to stand with Ukraine or are you going to stand with Putin? Are you going to stand with America or Trump?”

According to a report in the Financial Times, NATO will announce on Wednesday that 18 of its 31 members will meet their defense budget targets of 2% of GDP this year.

Among NATO members, only one — Poland — spends a larger share of its GDP on defense than the United States.

In 2016, only five NATO members met the same target, prompting sharp criticism of Mr Trump, who has repeatedly suggested the US might withdraw from the alliance.

The spat between Mr Biden and Mr Trump over Ukraine aid and US-NATO relations has highlighted one of the defining divisions of the upcoming presidential election.

Mr Biden has often cast the US as a key participant in a generational global conflict between democracies and autocracies.

In his view, Ukraine is one of the main battlegrounds of this conflict, and European allies in NATO and the EU are key partners.

During his four years as president, Mr Trump has often downplayed US participation in any kind of multilateral alliances, focusing instead on direct relations with other countries and their leaders.

He suggested that NATO and other US allies are expendable if they do not directly advance US interests.

The package approved by the Senate early on Tuesday includes $60bn for Ukraine, $8bn for Taiwan and other US allies in Asia, $14bn for Israel's war against Hamas and $10bn for humanitarian aid in conflict zones, including Gaza.

It had the support of 22 Republican senators, but faced considerable opposition from conservative lawmakers who oppose sending more funds overseas until the government can deal with the growing number of migrants at the southern US border.

An earlier attempt to pass a $118 billion aid package that included border security measures collapsed after criticism from Mr Trump.