WASHINGTON — American-made semiconductors and other parts have been found in Russian weapons used against Ukraine, even with strict Biden administration sanctions, experts told a Senate panel Tuesday.

“American manufacturers are fueling and supporting the growing and gargantuan Russian war machine,” Sen. Richard Blumenthal, D-Conn., said in a hearing by the Senate Homeland Security & Governmental Affairs Committee’s investigations subcommittee. “Our sanctions system is a sieve, our export control regime is lethally ineffective, and something has to be done.”

Blumenthal, the chair of the investigations panel, said Ukrainian President Volodymyr Zelenskyy handed him a folder during the senator’s visit to Ukraine last weekend containing evidence of American components being used against Ukrainians.

Included in this folder, the senator said, was a list of 211 chips, semiconductors and other technology embedded in missiles and other military products used by the Russians to kill Ukrainians.

Of these 211 pieces, Blumenthal said 87 were made by four U.S. companies: Intel, Analog Devices, AMD and Texas Instruments.

The four companies have been scrutinized by the subcommittee because they increased shipments of their products to countries likely being used by Russia to avoid United States export controls — including Georgia, Kazakhstan and Turkey — since the Russian invasion of Ukraine two years ago.

The Biden administration halted direct exports of semiconductors to Russia and exports of foreign-made products that use American technology in 2022.

Semiconductors are the brains of almost all modern weapons, and the United States is the most sophisticated manufacturer, according to James Byrne, the director of the Open Source Intelligence and Analysis Research Group of The Royal United Services Institute for Defence and Security Studies.

“It is technology that fits into those systems, and the Russians cannot simply replace,” Byrne said during the hearing. “In that sense, we have great leverage.”

The parts are likely being sent to Russia from countries not subject to U.S. export controls, including Russian border states, said Elina Ribakova, senior fellow at the Peterson Institute for International Economics, a nonprofit research organization based in Washington, D.C. She also is vice president for foreign policy at the Kyiv School of Economics.

Byrne stressed that, though export controls and sanctions are difficult to enforce, this leverage that the United States has in the semiconductor business means that the government should do its best to tighten restrictions.

But the existing limitations have not stopped Russia from obtaining this technology, according to Damien Spleeters, deputy director of operations for Conflict Armament Research, a British-based organization that tracks weapons and ammunition in war zones.

Spleeters said some components found in Russian military equipment were made before 2022, implying that the country was stockpiling before the invasion. Now, his organization is finding more pieces that were produced after the Russian invasion.

Over 70% of foreign components in Russian weapons is manufactured in the United States, according to Ukraine’s National Agency on Corruption Prevention.

Though there was a drop immediately after the invasion, Russian imports of battlefield goods were only 10% less than before the full-scale invasion of Ukraine, according to data from the Kyiv School of Economics.

“Russia has been so successful in evading U.S. export controls that its ability to import critical battlefield goods nearly recovered to levels seen before the invasion of Ukraine,” Blumenthal said. “That status quo is unacceptable.”

Russia isn’t alone in using American-manufactured components in their weapons systems. Iran and North Korea also use American parts in their weapons, Spleeters said.

To stop the import of such products to Russia and other U.S. adversaries, experts urged the government to focus on tracking where products are being distributed to and figuring out how to close loopholes in the sanctions system.

Ribakova wrote in a Financial Times opinion piece Tuesday that “the consequences of non-compliance must be strong enough to affect companies.”

The hearing came days after the United States announced hundreds of new sanctions against Russia.