The Reagan administration today is expected to offer federal funds to begin a huge project deepening the Baltimore Harbor for giant coal hauling ships, according to congressional sources.

President Reagan is reportedly prepared to set aside fiscal 1983 funds that Maryland would be expected to pay back, perhaps through user fees. The plan, which would require congressional and state approval, is expected to face opposition from major ports across the country that are also seeking to expand. Only Baltimore is expected to receive the federal help, according to sources.

Assistant presidential press secretary Mark Weinberg yesterday would confirm only that Reagan will meet today with Sen. Charles McC. Mathias (R-Md.) and Rep. Marjorie Holt (R-Md.) and that the harbor project is "a possible topic." Sen. Mathias has been active in efforts to expand the Baltimore Harbor's potential for deeper draft ships.

Maryland Port Administrator W. Gregory Halpin confirmed the nature of the meeting, saying, "We're very happy about it."

The entire project, an ambitious effort to dredge 72 million cubic yards from Baltimore's shipping channels, is expected to cost $332.5 million, according to Halpin. He said Maryland would be ultimately responsible for paying for the operation.

The dredging would deepen the channels from 42 to 50 feet, enabling the latest generation of 80,000 ton cargo ships to use the harbor when fully loaded, said Halpin. Currently, ships no larger than 55,000 tons can use the port.

An inability to handle substantially increased foreign demand for U.S. coal has hampered many of the nation's major ports. A source indicated that Reagan's decision was influenced by this, and by a desire to offset western demands for Soviet natural gas.

Mathias mirrored that assessment and recalled a conversation with an Italian cabinet member who told him, "If you don't want us to use Soviet energy, you have to give us an alternative."

"Getting the Baltimore project started is important to the national interest since it will open up one of the country's major coal export ports to deeper draft vessels," Halpin said.

If approved, the plan will enable the Army Corps of Engineers to begin dredging as early as the second quarter of fiscal 1983. Dredging could be finished "in four years, on a fast-track basis," according to Halpin, but others indicated that it could take several years longer to complete.

Halpin and Mathias said plans for such expansion gained federal approval in 1971, but have been blocked by litigation by citizens concerned about environmental effects and a split in the Maryland delegation.