By Valerie Volcovici

NEW YORK (Reuters) - The Biden administration is working on plans to bring additional decommissioned nuclear power reactors back online to help meet soaring demand for emissions-free electricity, White House climate adviser Ali Zaidi said on Monday.

Two such projects are already underway, including the planned recommissioning of Holtec's Palisades nuclear plant in Michigan and the potential restart of a unit at Constellation Energy's Three Mile Island plant in Pennsylvania, near the site of the worst nuclear accident in U.S. history.

Asked if additional shuttered plants could be restarted, Zaidi said: "We're working on it in a very concrete way. There are two that I can think of."

He declined to identify the power plants or provide further details about the effort.

Speaking at the Reuters Sustainability conference in New York, Zaidi said repowering existing dormant nuclear plants was part of a three-pronged strategy of President Joe Biden's administration to bring more nuclear power online to fight climate change and boost production.

The other two prongs include development of small modular reactors (SMRs) for certain applications, and continuing development of next generation, advanced nuclear reactors.

Biden has called for a tripling of U.S. nuclear power capacity to fuel energy demand that is accelerating in part due to expansion of power hungry technologies like artificial intelligence and cloud computing.

Last week, the Biden administration said it closed a $1.52 billion loan to resurrect the Palisades nuclear plant in Michigan, which would take two years to re-open.

Constellation and Microsoft, meanwhile, signed a power deal last month to help resurrect a unit of the Pennsylvania plant, which Constellation hopes will also receive government support.

Zaidi told the conference that the U.S. Navy on Monday had requested information to build SMRs on a half dozen bases. "SMR is a technology that is not a decades-away play. It's one that companies in the United States are looking to deploy in this decade," he said.

Zaidi also addressed the woes that have beset a separate Biden clean energy goal, to bring 30 gigawatts of offshore wind capacity online by the end of the decade.

The administration shelved offshore wind lease sales this year in both Oregon and the Gulf of Mexico due to low demand from companies, as high costs, equipment issues and supply chain challenges hit other projects.

Zaidi said at least half of the 30GW goal is already under construction and that some of the early snags provide helpful learning for future projects.

"I am pretty optimistic about the next of wave of projects where we will have a domestic supply chain and hopefully better cost to capital relative to what projects are facing right now," he said.

(Reporting by Valerie Volcovici; Editing by Bill Berkrot)