President Donald Trump has warned that the US will bolster its nuclear arsenal to put pressure on Russia and China.

Speaking to reporters, he repeated his belief that Russia has violated the 1987 Intermediate-Range Nuclear Forces (INF) treaty, which he has threatened to leave. Russia denies this.

The Cold War-era treaty banned medium-range missiles, reducing the perceived Soviet threat to European nations.

Russia has warned it will respond in kind if the US develops more weapons.

Mr Trump said the US would build up its arsenal "until people come to their senses"

He added: "It's a threat to whoever you want to include China and it includes Russia and it includes anybody else that wants to play that game... [Russia has] not adhered to the spirit of that agreement or to the agreement itself."

Meanwhile, US National Security Adviser John Bolton has been holding talks in Moscow after Russia condemned the US plan to quit the deal.

Mr Bolton was told that the US withdrawal would be a "serious blow" to the non-proliferation regime.

However, Russia's Security Council Secretary Nikolai Patrushev also said the Kremlin was "ready" to work with the US to remove "mutual" grievances over the INF.

As Mr Bolton began his visit, Moscow warned it would take steps to maintain the balance of nuclear power. (BBC)