Shiite rebels backed by supporters of former president Ali Abdullah Saleh have taken over Yemen's third largest city of Taiz and its airport.
The Houthi soldiers opposed to Yemen's president, Abd-Rabbu Mansour Hadi, seized large parts of the city which is located between the country's capital Sanaa and the second city of Aden.
The seizure follows a call from the Houthis rebels for a general uprising against forces loyal to Hadi, who has established a base in Aden after fleeing the capital.
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The letter was signed by the CBI, British Chambers of Commerce, the EEF, the Institute of Directors and the Federation of Small Businesses.
A spokesperson said Rory Stewart's remarks were in line with the British government’s stated position.
The minister's intervention will come a week after Trump decertified the landmark agreement claiming it was not in the US national interest.