A bipartisan group of 10 senators has put a hold on the nomination of Robert K. Dawson to head the U.S. Army Corps of Engineers, saying they are concerned that his confirmation "will mean the end of the federal government's regulatory role in the conservation of wetlands."

The action is the latest and most severe setback for Dawson, who has served as assistant Army secretary for civil works on an acting basis for more than a year and was second in command for four years before that.

In a telephone interview yesterday, Dawson said he expected to be confirmed despite the opposition, which he attributed to "a difference of opinion."

But his candidacy has run into an unrelenting thunder-squall of opposition, first from environmental groups and later from the Senate Environment and Public Works Committee. At the heart of the controversy is the Corps' record of protecting environmentally sensitive marshes and bogs, which are vanishing at a high rate despite their importance to wildlife and water quality.

Environmentalists contend that, under Dawson's stewardship, the Corps has virtually abandoned its responsibility under the Clean Water Act to protect wetlands from drainage and development. Even the National Wildlife Federation, which in nearly 50 years of existence had never opposed a presidential nominee to an executive agency, blistered Dawson in testimony prepared for his confirmation hearing last month.

Despite the opposition, the Armed Services Committee approved the nomination, 13 to 1, with five members voting "present."

But in a letter this week to Majority Leader Robert J. Dole (R-Kan.), six Republican and four Democratic senators warned that there will be an "extended debate" if the nomination is brought to the floor.

"It is our hope that the question never comes to a vote in the Senate," the senators wrote, charging that Dawson has "effectively dismantled . . . the most important regulatory program the federal government has to curb the loss of the nation's fast-disappearing wetlands."

The letter was signed by Republicans John H. Chafee (R.I.), Robert T. Stafford (Vt.), Gordon J. Humphrey (N.H.), David F. Durenberger (Minn.), John Heinz (Pa.) and Robert W. Kasten Jr. (Wis.). The Democrats were George J. Mitchell (Maine), John F. Kerry (Mass.), Patrick J. Leahy (Vt.), and William Proxmire (Wis.).

Stafford is chairman of the Environment and Public Works Committee, and Chafee is chairman of its environmental pollution subcommittee, which has jurisdiction over the Clean Water Act and its wetlands protection program, but not over Dawson's nomination. Humphrey, Durenberger and Mitchell are members of the committee and subcommittee.

Opposition to Dawson's nomination stiffened in the committee after hearings this year in which Dawson informed senators that he did not believe Congress intended to protect wetlands under the Clean Water Act.

"It's just a disagreement over the administration's policy in this area," Dawson said yesterday. "We are trying to give the regulated public some relief. If we do it carefully, it can be an environmental plus. A program like this relies heavily on voluntary compliance."

The Corps' record also has been criticized within the administration, however. Both the Environmental Protection Agency and the Interior Department, which share jurisdiction over wetlands, have quarreled with the Army's streamlined regulatory program. In a letter to Dawson last year, former assistant Interior secretary G. Ray Arnett called the program "so flawed it is no longer a usable tool to adequately protect wetlands."