British Prime Minister Keir Starmer arrived in Ukraine Thursday with a pledge to help guarantee the country’s security for a century, days before Donald Trump is sworn in as U.S. president.

The UK and Poland will start work on a new defence and security agreement on Friday, when Sir Keir Starmer travels to the eastern European country for talks. The Prime Minister has said that it is “time to take our partnership to the next level” with Warsaw and that “closer collaboration” with allies such as Poland will “protect the UK’s national security”.

It comes after the prime minister visited Ukraine for the first time since his party's election victory in July.