US President Joe Biden promised a new $625-million security assistance package to Ukraine on Tuesday, prompting a warning from Moscow that such a move risked a direct military clash between Russia and the West.
The US package would include High Mobility Artillery Rocket System (HIMARS) launchers used in Ukraine's successful counter-offensive where it has recently forced Russian troops into retreat.
In a telephone call with Ukrainian President Volodymyr Zelenskiy and Vice President Kamala Harris, Biden underscored that Washington would never recognize Russia's annexation of Ukrainian territory, the White House said in a statement.
Biden "pledged to continue supporting Ukraine as it defends itself from Russian aggression for as long as it takes."
The aid package is the first since Russia's most recent declared annexation of Ukrainian territory and the second Presidential Drawdown Authority (PDA) since Ukraine's large battlefield gains in mid-September.
In a strongly worded response, Russia's envoy to the United States warned that Biden's offer fueled the danger of a direct military clash between Russia and the West.
On the Telegram messaging app, Ambassador Anatoly Antonov urged Washington to stop "provocative actions" that could lead to "serious consequences".
"We perceive this as an immediate threat to the strategic interests of our country," he said.
Russia's declared annexations last week followed what it called referendums in occupied areas of Ukraine. Western governments and Kyiv said the votes breached international law and were coercive and non-representative.
The State Department said in a release the package includes four HIMARS launchers and associated rockets, 32 Howitzers with 75,000 rounds of ammunition, 200 Mine-Resistant Ambush Protected (MRAP) vehicles, and Claymore anti-personnel mines.
Made by Lockheed Martin Corp, the HIMARS launchers' accuracy and longer range have allowed Kyiv to reduce Russia's artillery advantage.
"Recent developments from Russia's sham referenda and attempted annexation to new revelations of brutality against civilians in Ukrainian territory formerly controlled by Russia only strengthens our resolve," the US Secretary of State Antony Blinken said in a statement.
Last week, the United States unveiled a $1.1 billion arms package for Ukraine, which included 18 HIMARS launcher systems, accompanying munitions, various types of counter drone systems and radar systems.
But last week's aid package was funded by the Ukraine Security Assistance Initiative (USAI) meaning the government has to procure the weapons from industry, rather than pulling them from existing US weapons stocks.
The United States has now pledged 20 HIMARS launchers to Ukraine using PDA.
This announcement would mark more than $16.8 billion worth of US security assistance since Russia invaded Ukraine on Feb. 24.