In a sharply worded letter to Interior Secretary James G. Watt, the governors of nine western states have called his department's new coal-leasing policies a move "to once again centralize on the Potomac critical decisions affecting western states."

The governors, seven Democrats and two Republicans, said that the new regulations would reduce the influence of state officials and open the way for "excessive leasing of federal coal."

This could drive down the price the government receives for its resources and lead to "needless, delaying litigation that will not serve the interests of the federal government, the affected states, the energy industry or the energy consumer," the letter said.

Interior officials declined to comment on the letter, saying Watt had not yet received it. The Washington Post has obtained a copy of it.

The letter was signed Monday at a western governors' meeting in Idaho, where the same nine officials unanimously passed a resolution critical of the Reagan administration proposal to sell millions of acres of public lands to help retire the national debt.

The resolution and the letter represent unusually sharp criticism by the governors, often cited by Watt as his strong supporters and who have praised many of his pro-development policies. Watt's policies directly affect the nine governors' states, where Interior owns more than one-third of the land and much of the coal.

The governors who signed the letter and the resolution are Ed Herschler of Wyoming, Richard D. Lamm of Colorado, Scott M. Matheson of Utah, Ted Schwinden of Montana, Bruce King of New Mexico, Allen I. Olson of North Dakota, John V. Evans of Idaho, William Janklow of South Dakota and Bruce Babbitt of Arizona. Janklow and Olson are Republicans.

In an interview published in July in Human Events magazine, Watt said of the western governors: "We have the full support of all those governors, which drives the Democrats among them up the wall . . . . They don't have one reason to be against me, and are not against me." Watt also said that Babbitt and Lamm "are both liberal Democrats who have supported me without exception."

The new coal regulations have been in effect for only five weeks and have not yet been used in a major sale of federal coal rights. Interior revised the rules as part of the Reagan administration's effort to "eliminate burdensome and unnecessary rules," according to a July 30 press release.

The release also said the new regulations would increase the governors' role in leasing decisions.

Western governors proposed 175 changes when Interior circulated a draft of the new rules earlier in the year. Interior rejected 159 of them, according to the governors' aides.

The main charge in the letter was that the regulations "eviscerate the most vital organ for state/federal cooperation, the regional coal teams." The teams, composed of governors and Interior officials, were among the Carter administration's more popular initiatives among westerners.

The governors had recommended that Interior retain the old system, under which the regional coal teams recommended how much coal should be auctioned off at a time and where the development should take place.

The Interior secretary made his decision after receiving the recommendations.

Under the new regulations, the teams will forward several options, rather than one, to Watt. Aides to the governors said they fear Interior will put more coal on the market than state officials want.

They cited a recent proposal by Interior to lease between 800 million and 1.2 billion tons of coal along the Montana-North Dakota border, after a regional coal team recommended leasing between 400 million and 800 million tons.

"We don't want to stop coal leasing by any means, but we're afraid these guys may be pushing too hard," said DeWitt John, an official of the Colorado Department of Natural Resources.

Interior came under fire earlier this year after a record-breaking sale of federal coal rights along the Wyo-ming-Montana border.

The sale came during a glut in the coal market, and drew little competition from mining companies. Interior officials defended the timing of the sale, saying it is not up to the government to manipulate the coal market.

The governors said in their letter that Interior's policies "appear to be the product of a misconception that the department can ignore the marketplace in making its coal leasing decisions.

"We believe the marketplace must work, and the only way it can is if the federal government takes a businesslike approach to coal leasing."