The United States toughened its messaging on the Ukraine war on Monday, saying the American aim was not just to thwart the Russian invasion but also to weaken Russia so it could no longer carry out such military aggression anywhere.

The aim was stated in explicit terms by the highest-ranking Biden administration delegation to visit Ukraine since the war began. It reflected an emboldened intent to counter Russia by giving more numerous and powerful arms to the Ukrainians, who have battled Russian forces with unexpected tenacity, sapped Kremlin resources and flustered Russian President Vladimir Putin’s hope for a quick victory.

The American delegation also announced that the United States would reopen its embassy in the Ukrainian capital, Kyiv — another signal aimed at portraying Russia as headed toward defeat. The embassy, closed in the run-up to the Feb. 24 invasion, will be led by a newly appointed ambassador.