Lott noted during a press briefing that one option is to amend a Senate bill with language reining in the FCC.

The lawmakers want the agency to complete a separate proceeding on localism -- the levels of local news and civic programming that television stations air -- before holding the vote. FCC Chairman Kevin Martin has indicated that localism might be addressed as part of the agency's broader ownership review. Dorgan complained about the apparent decision to fast-track the vote, saying "the accelerated pace is a surprise to everybody."

Lott said he came to Washington as a "deregulator" but has become increasingly worried about media consolidation. "I just don't think this is in the people's best interests," he said.

"The chairman has proposed a schedule which he is seeking consensus on," an FCC spokeswoman responded, adding that "we take concerns from members of Congress very seriously." The agency tentatively plans to hold an Oct. 31 hearing in Washington on localism and a Nov. 2 hearing in Seattle on media ownership.

An FCC official predicted that the congressional pressure would have an impact. "He will clearly have to take steps to reduce the heat he's going to face," the source said of Martin.

The agency faced a similar congressional backlash in 2003. Most of the changes approved then on a 3-2 party-line vote were later rescinded by an appeals court.

Senators are particularly incensed that the Republican-controlled FCC might loosen the federal ban on ownership of newspaper and broadcast outlets in the same market. The prohibition has been in effect since 1975, but combinations predating the ban have been grandfathered and some temporary waivers have been granted.

The FCC official said Martin also might increase the number of radio properties one company can own in a market and permit duopolies -- ownership of two TV stations by one entity -- in large cities. Duopolies are now permitted in small markets.

Dorgan and Lott have support from other powerful players, including Sen. Barack Obama of Illinois, one of the leading Democratic presidential contenders, who urged the agency in a Monday letter to allow an independent panel to develop proposals to foster diverse ownership of media outlets.

During a Wednesday hearing before the Senate Commerce Committee, Missouri Democratic Sen. Claire McCaskill said she has "heart palpitations" about large conglomerates dominating the radio and television businesses. Derek Turner, research director of the advocacy group Free Press, accused the FCC of lacking "even the most basic understanding of what the true state of female and minority ownership is."

House Energy and Commerce Chairman John Dingell, D-Mich., and Telecommunications and the Internet Subcommittee Chairman Edward Markey, D-Mass., issued statements Monday urging the FCC to provide adequate time for review.