American and Ukrainian military leaders are searching for a new strategy that they can begin executing early next year to revive Kyiv’s fortunes and flagging support for the country’s war against Russia, according to U.S. and Ukrainian officials.

The push for a fresh approach comes after Ukraine’s monthslong counteroffensive failed in its goal of retaking territory lost to the invading Russian army and after weeks of often tense encounters between top American officials and their Ukrainian counterparts.

President Volodymyr Zelensky of Ukraine arrived in Washington on Monday for hastily arranged meetings this week with President Biden and Congress to discuss the way forward. The two presidents will attempt to demonstrate solidarity and bolster support for Ukraine at a critical moment, both on the battlefield and on Capitol Hill.

Ukraine’s setbacks have come as Republican support for continuing American financial assistance for Kyiv has eroded. Even some senior U.S. officials have expressed worries that if the war falls into a long stalemate next year, President Vladimir V. Putin of Russia will gain the advantage.