There are "logistical challenges, especially moving natural gas," says Washington, which is holding talks with companies over a potential diversion of energy supplies to Europe if Russia invades Ukraine.
US has faced challenges in finding alternative sources of energy supplies to Europe if Russia invades Ukraine and energy flows from Russia are interrupted, the White House said but pledged to continue talks with companies and countries.
"There is no question there are logistical challenges, especially moving natural gas," White House press secretary Jen Psaki told reporters on Wednesday when asked about reports that the industry had little or no capacity to provide the required energy supplies.
"That's part of our discussions with a lot of companies and countries," she said.
"But again, these conversations are ongoing and we don't intend to fail."
Energy crisis amid invasion fear
Senior Biden administration officials on Tuesday said the United States was in talks with major energy-producing countries and companies in North Africa, the Middle East, Asia and the United States over a potential diversion of supplies to Europe if Russia invades Ukraine.
Psaki said she had no announcements to make, but said the objective was clearly to mitigate against the potential regional and global consequences of a disruption in energy supplies and ensure that sufficient supplies were available.
The European Union depends on Russia for around a third of its gas supplies.
Moscow could reduce supplies to the EU, which would send the bloc's already sky-high energy bills soaring even further in the middle of winter.
"Europe does not have the same room to manoeuvre" as Washington, said Olivier Dorgans, a lawyer at the Ashurst law firm who specialises in economic sanctions.
The bloc risks "sanctioning itself", Dorgans said.
"Geographic proximity goes hand in hand with close economic and security implications and ties," Guntram Wolff, director of the Bruegel think tank in Brussels, told the AFP news agency.
Wolff said the EU has gas reserves that would last just "a couple" of weeks if Russia were to turn off the tap.
He said the EU could try to compensate with gas from Qatar, a close US ally with huge reserves. It is also the world's biggest exporter of liquified natural gas.
US responds to Russia's demands, seeks dialogue
Also on Wednesday, the United States delivered written replies to sweeping Russian security demands, a key step in a fragile diplomatic process as Russia staged new military drills on land and sea near Ukraine.
Washington has made clear that Russian demands for NATO to pull back troops and weapons from eastern Europe and bar Ukraine from ever joining are non-starters but says it is ready to discuss other topics such as arms control and confidence-building measures.
Whether President Vladimir Putin is prepared to accept that limited agenda will determine the next phase of the crisis, in which Moscow has massed around 100,000 troops near the border with Ukraine while denying it plans to invade its neighbour.