Donald Trump's suggestion the US would not protect Nato allies failing to spend enough on defence "undermines all of our security", the Western military alliance's chief has said, Ednews reports citing BBC.

Jens Stoltenberg also suggested it put US and European troops at greater risk.

The Republican said he had told allies he would "encourage" Russia to attack any Nato member that failed to meet the alliance's target of 2% of their GDP.

Members of NATO commit to defend any nation in the bloc that gets attacked.

President Joe Biden called Mr Trump's comments "appalling and dangerous", suggesting his predecessor intended to give Russian President Vladimir Putin "a green light for more war and violence".

Addressing crowds during a rally in South Carolina on Saturday, Mr Trump said he had made his comments about Russia during a previous meeting of leaders of NATO countries.

The former president recalled that the leader of a "big country" had presented a hypothetical situation in which he was not meeting his financial obligations within NATO and had come under attack from Moscow.

The frontrunner for the Republican nomination for this year's presidential election did not make clear which nation or leader he was speaking about, or even when this conversation took place.

According to NATO's own figures for 2023 spending, 19 of its 30 member nations are spending below the target of 2% of their annual GDP on defence - among them Germany, Norway and France.

But most countries which border Ukraine, Russia, or its neighbour and ally Belarus, are exceeding this guideline.

At over 3.9% of its annual GDP, Poland spends even more than the US. Romania, Hungary, Finland and the Baltic states of Latvia, Lithuania and Estonia range between 2.3 and 2.7% for defence expenditure.

In a statement on Sunday, Mr Stoltenberg emphasised the alliance remains "ready and able" to defend its members and any attack "will be met with a united and forceful response".

But he said any suggestion that "allies will not defend each other undermines all of our security", and suggested Mr Trump's remarks "put American and European soldiers at increased risk".

"I expect that regardless of who wins the presidential election the US will remain a strong and committed NATO ally," he added.