US Secretary of State Rex Tillerson has discussed the need to increase diplomatic pressure on North Korea with UK Prime Minister Theresa May in London, where the Iran nuclear deal was also raised.

Axar.az reports citing Press TV.

The top US diplomat "never misses an opportunity in bilateral, multilateral settings to raise North Korea and the need to increase pressure on North Korea," Tillerson's policy adviser Brian Hook said Thursday.

The two discussed North Korea's "destabilizing activities" and the importance of the international community coming together to put pressure on Pyongyang, May's spokesman said.

On September 3, North Korea detonated its sixth and most powerful nuclear test to date, prompting the UN Security Council to implement new sanctions.

On the Iran nuclear agreement, which is viewed skeptically by US President Donald Trump, May was "underlining its importance in preventing Iran from procuring nuclear weapons," her spokesman said.

Tillerson also held a news conference with his British counterpart Boris Johnson on Thursday, where they held talks about Iran and North Korea.

"The Trump administration is continuing to review and develop its policy on Iran ... no decision has been made," Tillerson said during the news conference.

"President Trump has made it clear ... we must take in to account the totality of Iranian threats, not just Iran's nuclear capabilities, that is just one piece of our posture towards Iran."

In a statement issued Wednesday, over 80 prominent international disarmament experts urged Trump to reconsider his possible plans to unravel Iran’s 2015 nuclear agreement with six world powers, including the US.

Trump, who made no secret of opposing the nuclear agreement in his election campaign, has threatened to “tear up” the agreement, calling it “the worst deal ever negotiated.”

On Monday, the IAEA, however, once again confirmed that Iran has lived up to its commitments under the landmark nuclear agreement.

Tehran says it plans to adhere to the nuclear deal regardless of any probable US decision to withdraw from the agreement.