U.K. Prime Minister Keir Starmer told a virtual gathering of the so-called “Coalition of the Willing” that London’s support for Kyiv remains “unwavering” and that any cease-fire negotiations must be coupled with “credible” security guarantees for Ukraine. He said military plans were ready to be activated should a truce take hold and stressed that international borders “must not be changed by force.” Starmer said he had discussed the outlines of such guarantees earlier in the day with former U.S. President Donald Trump and with European leaders, reporting “progress” in the talks. According to Ukrainian President Volodymyr Zelenskiy, Trump signaled support for providing long-term assurances once a peace settlement is reached. The U.K. leader added that Britain is prepared to intensify economic pressure on Moscow, including fresh sanctions, if Russia fails to engage constructively. Starmer called for diplomacy to be paired with sustained military assistance to Kyiv to deter further Russian aggression.