The foreign secretary, Jeremy Hunt, has agreed to attend a summit organised by the US in Warsaw originally billed as an alliance to confront Iranian aggression, but only on the condition that the US secretary of state hosts a meeting on Yemen on the summit’s margins.

Hunt is the first senior European minister to declare that he will attend the summit, which starts on 13 February. European diplomats have been reluctant to attend, suspecting that the event is part of a US drive to undermine Europe’s support for the Iran nuclear deal signed in 2015.

The EU shares Washington’s concerns about many aspects of Iranian behaviour but has been at loggerheads with the Trump administration over the US pullout from the nuclear deal and the subsequent imposition of US secondary sanctions on any firms that seek to trade with Iran or purchase its oil exports. The EU is due to publish long-delayed and technically fraught plans to circumvent US sanctions.

Washington had called on ministers from 70 countries to attend the summit. Faced by the European reluctance to join a two-day event exclusively attacking Iran, US diplomats were forced to broaden the agenda to include wider issues in the Middle East.

Hunt, after talks with the secretary of state, Mike Pompeo, in Washington this week, has agreed to attend, but only on the condition that the UK, US, United Arab Emirates and Saudi Arabia hold a meeting on the margins about Yemen. The UAE and Saudi are key backers of the government of Abd Rabbu Mansour Hadi, who is fighting a Houthi rebellion.

The meeting helps avoid a rare UK-US standoff and gives Hunt a chance to hear about the chances of salvaging a UN-sponsored ceasefire agreed in Stockholm last month.

There are ever louder claims by Saudi Arabia that Houthis are ignoring the ceasefire terms. The ceasefire prevented a Saudi-sponsored assault on the port city of Hodeidah. The port is critical to the supply of aid into Yemen.

The Hadi government claims to have documented more than 400 breaches of the ceasefire and wants the UN special envoy Martin Griffiths to declare that Houthis are not abiding by it.

Griffiths was in Sana’a, the Houthi-held capital of Yemen, for talks this week and has been trying to agree clearer arrangements for the control of Hodeidah port and for a civilian security force to run the city. The Houthis and the Saudis have different interpretations of how the civilian force should be composed.