BRUSSELS, March 21 (Reuters) - New U.S. funding to boost domestic nuclear fuel production is a historic step but the world's nuclear consumers must also shift supply chains to meet the goal of loosening Russia's grip on the industry, a U.S. Department of Energy (DoE) official said.

At the COP 28 climate conference, the United States along with Japan, France, Canada and the UK committed to raising $4.2 billion in government funding for nuclear power.

Kathryn Huff, assistant secretary on nuclear at the DoE, told Reuters at a nuclear summit in Brussels that the countries jointly tried to identify the amount of investment needed from governments to support the fuel supply chain.

"The $2.7 billion is the U.S. part of that contribution...It's a historic step in the fuel supply chain but of course we see an opportunity to go further," she said.

President Joe Biden signed a bill approving the $2.7 billion in U.S. funding for domestic fuel production this month.

The funded programmes include uranium fuel enrichment such as high assay low enriched, or HALEU, uranium fuel, which is expected to be used in high tech nuclear plants. These new reactors can be much smaller with longer operating cycles.

Huff added that the success of shifting supply chains would also hinge on other nations moving to these "trusted sources rather than sources that could leverage supply against them, like Russia."

Russian state-owned energy company Rosatom says it supplies 17% of the world’s nuclear fuel. The U.S., the largest producer of nuclear energy, relies on Russia for 20% of its enriched uranium, although that is limited by an import cap that pre-dates Russia's invasion of Ukraine.

"(It's) a dependency we urgently need to divest ourselves from," Huff said. "We are looking at a way to begin import restrictions from Russia."

The U.S. has more than 90 operational nuclear reactors many of which are reaching the end of their 40-year lifespans. Only six so far have been approved to extend operations to 80 years.

A pilot programme in Ohio successfully produced HALEU and a request for proposals was launched in January. Today's nuclear plants typically rely on uranium enriched to 5% purity.

Congress is also poised to cut imports of Russian uranium, as part of Washington's response to Moscow's full scale invasion of Ukraine. U.S. Energy Secretary Jennifer Granholm said this week that a ban would free up funding to develop the domestic nuclear fuel market. (Reporting by Julia Payne, additional reporting by Timothy Gardner in Washington, Editing by William Maclean)