The U.S. will stand by Ukraine until its security sovereignty is guaranteed, Secretary of State Antony Blinken pledged on Tuesday in a visit to Kyiv, at a time when Russia is mounting fresh attacks in the country's east.

The top U.S. diplomat is the first senior U.S. official to travel to Ukraine after U.S. Congress passed a $61 billion military aid package last month following a delay of several months during which Russia gained advantage on the battlefield.

In a policy speech at Igor Sikorsky Kyiv Polytechnic Institute, Blinken acknowledged that the delay of U.S. weapons made Ukraine more vulnerable to Russia's attacks but said Kyiv can count on Washington's unwavering support because the American people understood that Russia will not stop in Ukraine.