The Americans are deeply concerned about advances in North Korea's weapons technology, they believe it could well be capable of hitting the United States with a nuclear warhead before the end of President Trump's first term. Any US military intervention to pre-empt that would be fraught with risk, but Mr Trump has toughened his rhetoric to drive home a message that it's a credible threat.

 

A key part of his plan is to pressure China to lean more heavily on North Korea to dismantle its nuclear weapons programme. The statement says the US is open to negotiations towards that end, but many even in Washington doubt the regime could ever accept such terms.

Democratic Senator Christopher Coons told reporters that military options were discussed at the special presidential briefing for senators.
"It was a sobering briefing in which it was clear just how much thought and planning was going into preparing military options if called for - and a diplomatic strategy that strikes me as clear-eyed and well-proportioned to the threat," he said.

A White House official said an option under consideration was to put North Korea back on the state department's list of countries that sponsor terrorism.

Mr Trump's predecessor, Barack Obama, imposed sanctions over a year ago following a nuclear test and satellite launch by the North.

North Korean government property in America was frozen and US exports to, or investment in, North Korea was banned.

The order also greatly expanded powers to blacklist anyone, including non-Americans, dealing with North Korea.
The senators received a highly unusual briefing by the Trump administration on the seriousness of the threat from North Korea and the

president's strategy for dealing with it on Wednesday.

Earlier Admiral Harry Harris, head of US Pacific Command, said the US would be ready "with the best technology" to defeat any missile threat.
The deployment of Terminal High-Altitude Area Defense (Thaad) system in South Korea was aimed, he argued, at bringing North Korean leader Kim Jong-un "to his senses, not to his knees".

Adm Harris said he believed that North Korea would try to attack the US as soon as it had the military capabilities.

China says the deployment of Thaad will destabilise security and there have been protests in South Korea itself, where three people were injured in clashes with police as the system was being delivered to a former golf course on Wednesday.