The US has pledged it will insist North Korea gives up all its nuclear capabilities and is subject to strict verification before sanctions are lifted, as it attempts to allay concerns that President Donald Trump could settle for a quick compromise deal at his summit with North Korean leader Kim Jong Un on June 12.

“We will continue to implement all UN Security Council resolutions on North Korea,” Jim Mattis, US defence secretary, said after a meeting with his Japanese and South Korean colleagues in Singapore on Sunday. “North Korea will receive relief only when it demonstrates verifiable and irreversible steps to de-nuclearisation.”

Mr Mattis’s remarks come as diplomats and military officials openly question whether the goal of “complete, verifiable, irreversible de-nuclearisation” of the Korean peninsula, laid down by the UN Security Council and known under the acronym CVID, can ever be achieved.