WASHINGTON A bipartisan US congressional committee urged the White House on Monday to disclose details on whether Russia was sharing insight with China on how to defeat US weapons used on the battlefield in Ukraine.

In a letter to White House National Security Advisor Jake Sullivan seen by Reuters, the House of Representative's select committee on China warned that Russia's battlefield adaptations that undermine certain US weapon systems are "likely to proliferate" to China, including Russian electronic warfare countermeasures to US precision munitions.

"We should anticipate and indeed operate under the assumption that Russia is passing information about vulnerabilities or counters to American and allied weapons systems to the PRC [People's Republic of China]," the committee's Republican chair John Moolenaar and ranking Democrat Raja Krishnamoorthi wrote.

The lawmakers cited media and think tank reports about China's support for Russia's military industries and the "alarming levels of Russian adaptation" that have undermined the effectiveness of several unspecified US weapons systems.

They asked Sullivan to assess Russia's ability to mitigate and counter US weapons deployed in Ukraine, and the extent to which Moscow had shared "lessons-learned" with China, as well as any Chinese military efforts to mirror Russian military innovations.

The White House National Security Council did not respond immediately to a request for comment.

The US is Ukraine's biggest supporter and has provided more than US$50 billion in military aid since 2022 when the Russian invasion began.

Last Thursday, Washington announced a new security package for Ukraine worth US$225 million, which includes a Patriot missile battery, additional ammunition for high-mobility artillery rocket systems and missiles, among other items.

Nato last week described China as the "decisive enabler" of Russia's war effort, and called on Beijing, which entered a "no limits" partnership with Moscow days before its invasion of Ukraine in 2022, to stop supporting Russia's war.

China responded by calling the Nato comments biased and has previously said its support for Russia is all normal trade.

Some analysts contend that Europe's Nato members must boost their ability to deal with European security challenges to enable the US to focus on threats poised by China, including the dispute over Taiwan, the democratic island Beijing claims as its territory.

The Kremlin has said that US weapons bound for the battlefield, including of long-range ATACMS missiles and Abrams tanks, would not change the battlefield situation because Russian armed forces were constantly adapting to new types of weapons.

  - Reuters