Theresa May has warned Donald Trump against taking unilateral action against North Korea, arguing that the US president should instead try to work with international organisations and partners.

Ahead of a summit with Chinese President Xi Jinping later this week, Mr Trump warned at the weekend that “if China is not going to solve North Korea, we will”.

But Mrs May on Monday said that such threats were not helpful.

"I think what is crucial - and where we have been working, and will continue to work through the United Nations Security Council, through resolutions which we have supported there, and with the United States - is to encourage China to look at this issue of North Korea and to play a more significant role in terms of North Korea,” she said.

"I think that's where our attention should focus."

Mr Trump’s meeting with Mr Xi is expected to focus on North Korea, and on trade deals. The US wants China to take a more muscular stance on the rogue state, while China wants to avoid a trade war with the US.

Mr Trump’s National Security Council has prepared a report for the president with his options to deal with North Korea. The report, it was claimed on Sunday, was accelerated to have it ready before Mr Trump's summit with Mr Xi, and it includes a range of economic and military measures.