Ministers have committed to spend £170 million over the next year on humanitarian aid in Yemen.
The Arab world's poorest country is in the grips of a stalemated war and what the UN calls the worst humanitarian crisis, with 22 million people needing aid.
The new UK aid package will provide life-saving food, medicine, clean water and sanitation to millions of Yemenis facing disease and hunger.
The announcement follows pledges by Saudi Arabia and the United Arab Emirates to give 930 million dollars (£505m) to US humanitarian efforts in the country.
Minister for the Middle East Alistair Burt, speaking after a UN event in Geneva on the crisis, said: "There can be absolutely no room for complacency in tackling the world's worst humanitarian crisis.
"With no end to the conflict, the situation will deteriorate with the number of men, women and children at risk of starvation at an all-time high.
"That's why UK aid will provide enough food to meet immediate needs for 3.4 million people, and buy fuel to mill enough wheat to feed a million people for over a year.
"Our support will continue to improve nutrition and access to clean water and sanitation across the country."
-- Alistair Burt (@AlistairBurtUK) April 3, 2018
The Yemen conflict has so far killed more than 10,000 people over the past three years.
The conflict has its roots in the failure of a political transition supposed to bring stability to Yemen following the Arab Spring uprising.
Disillusioned with the transition, many ordinary Yemenis supported rebels, known as Houthis, who took over Sanaa in late 2014.
In 2015, an assault by Houthi rebels on the city of Aden prompted a Saudi-led multinational coalition to launch a military campaign.
Mr Burt added: "We are very clear, only a political agreement can bring an end to this humanitarian crisis.
"For the sake of all Yemenis, we urge all parties to return to the negotiating table to find an inclusive political solution, and the UK is continuing to do all it can diplomatically to ensure such an outcome."
Through existing aid to Gavi the UK is supporting the first vaccination campaign - for 1.1 million people against cholera - since the conflict in Yemen began.
In 2017/18, UK aid provided nutritional support for 1.7 million people, and clean water and sanitation for an expected 1.2 million people.