KYIV — Secretary of State Antony Blinken arrived Tuesday in Ukraine’s capital on a mission to display Washington’s continued support for the country’s faltering war effort, after months of congressional inaction choked off military assistance and weakened Ukraine’s ability to repel renewed Russian attacks.

Blinken’s two-day trip is the first high-level visit by a Biden administration official since Congress last month approved a $61 billion aid package for Ukraine after seven months of obstruction by Republicans. The visit was intended as a show of solidarity as the Pentagon speeds antiaircraft defenses, artillery and other key equipment into the country to try to stabilize Kyiv’s front lines. But officials concede that given Ukraine’s sizable challenges, its military may not regain a battlefield advantage before 2025 at the earliest.