A U.S. court on Monday issued warrants for the seizure of two luxury planes owned by Russian billionaire Roman Abramovich under U.S. measures imposed after Russia's invasion of Ukraine, court records showed.

But the U.S. government's likelihood of gaining control of the aircraft worth nearly $400 million was uncertain.

A Department of Justice official said the $350 million Boeing 787 Dreamliner and $60 million Gulfstream G650 ER were not in U.S. custody, and the official declined to say if the U.S. government knows their locations.

A federal judge in Manhattan issued the warrants on the grounds that recent flights violated U.S. export controls imposed after Russia's invasion of Ukraine in February. The U.S. Department of Commerce filed related administrative charges against Abramovich.

But the official said the warrants are likely to dissuade companies from helping to move the aircraft. U.S. authorities are seeking to pressure business leaders close to Russian President Vladimir Putin to get him to halt what Kremlin calls its "special military operation" in Ukraine.

A spokesperson for Abramovich did not immediately respond to a request for comment. Abramovich has denied having close ties to Putin.

The Commerce Department said that the Gulfstream flew from Istanbul to Moscow on March 12, left the following day for Tel Aviv and flew from Istanbul to Moscow again on March 15. The Boeing flew from Dubai to Moscow on March 4, the department said.

Because the planes were U.S.-made, and the flights took place after export restrictions went into effect, Abramovich, a Russian national, would have needed a license from Commerce to fly them to Russia. No licenses were requested, but an administration official told reporters the department's policy is to deny such requests.

The department may seek to fine Abramovich up to $328,121 per unlicensed flight, or nearly $1 million for the three flights, among other penalties.

"Russian oligarchs such as Abramovich will not be permitted to violate U.S. export regulations without consequence," Commerce official John Sonderman said in a statement.

Commerce in March moved to effectively ground Abramovich's Gulfstream, along with 99 other planes it said had recently traveled to Russia, for allegedly violating export controls.

Abramovich owns both planes through a series of shell companies registered in Cyprus, Jersey and the British Virgin Islands, prosecutors said. In February he reorganized the ownership structure to make his children the beneficiaries of a trust that ultimately owns both planes.

But he continued effectively to own and control the planes when they flew to Moscow the next month, according to the Commerce Department.

Abramovich, who helped mediate talks between Moscow and Kyiv during the early days of the war, has not personally been sanctioned by the United States. He has been sanctioned by the European Union and Britain.