The U.S. military said on Thursday a blast on Sunday near a UNESCO world heritage site in Yemen's capital city of Sanaa was caused by a Houthi missile and not an American airstrike.

Kyiv is working with allies on security guarantees akin to NATO's mutual protection pledge, Ukraine's president Volodymr Zelensky has said. Officials from Ukraine and allies the U.S., the U.K., France and Germany met in London on Thursday in a week when a peace proposal was produced which outlined an Article 5-like agreement which would be backed by Washington.

London discussions between the US, United Kingdom, Ukraine, France and Germany ended Wednesday without agreement on the terms of a potential peace deal — but with promises to keep talking, as Ukraine President Volodymyr Zelensky again insisted ceding Crimea to Russia was a non-starter.