President of the US Donald Trump has thanked China for helping to rein in North Korea and claimed international pressure on the nuclear-armed outlaw nation is beginning to work, marking a change in tone amid concerns that tensions with Pyongyang are escalating dangerously.

Trump made a point of praising Chinese President Xi Jinping for his efforts to squeeze Chinese ally North Korea economically and diplomatically. In other settings – usually Twitter – Trump has complained about lacklustre co-operation and suggested he could punish China economically if it did not do more.

“I applaud China for breaking off all banking relationships with North Korea, something that people would have thought unthinkable even two months ago.

I want to thank President Xi.”

Although the president repeated a threat of military action, his language was mild by comparison with his branding of North Korean leader Kim Jong-un as “a madman” and his vow last week to “totally destroy” North Korea if necessary to protect the US or its allies.

Trump also expressed confidence he could solve a decades-long impasse that has bedevilled his predecessors.

His remarks appear to reflect an attempt at lowering the temperature after days of rhetoric and threats from both sides.

During his first address to the UN last week, Trump repeated his dismissive nickname for Kim, “Rocket Man”, and shocked some diplomats with an open threat of warfare. The possibility of conflict appeared to worsen after the annual diplomatic gathering of the UN General Assembly, with the US launching a symbolic B-1 bomber flight off the North Korean coastline. North Korea’s top diplomat said on Monday that Trump had effectively declared war andPyongyang could shoot down a US warplane at will.

Trump’s statements closely echo the more diplomatic message being delivered in public and private by top administration officials, who present the threat of military action as part of a co-ordinated strategy to slow down North Korea’s weapons programme and impress upon Kim that these weapons are ultimately a liability. Treasury announced new sanctions on eight North Korean banks, 26 people in China and three other countries that the Trump administration says are linked to North Korean financial networks.

The penalties come on top of unilateral US sanctions announced last week, meant to close off the US financial system to Pyongyang and anyone doing business with it, as well as import and export restrictions since early August.

The Trump administration says there are signs that North Korea is starting to feel the pinch from international pressure, especially with the addition of restrictions on fuel oil and other forms of energy that will affect the ruling elite. – The Washington Post