Washington ? Key senators have unveiled plans to require dramatic increases in vehicle fuel economy, prompting a fight from automakers who say the proposals are a threat to increasingly popular and fuel-hungry light trucks.

Sen. John McCain of Arizona, senior Republican on the Senate Commerce Committee, introduced a plan Thursday that would require cars and light trucks to average 36 miles per gallon by 2016.

A Democratic plan introduced Friday by Sen. John Kerry of Massachusetts and the committee chairman, Sen. Ernest Hollings of South Carolina, would require a 35 mpg average by 2013.

The White House, preferring to set its own standards, is trying to organize Republican senators against these legislative proposals, a senior administration official said.

Currently, cars must attain an average of 27.5 mpg; light trucks, which include minivans, sport utility vehicles and pickups, must get 20.7 mpg.

Automakers don’t have to meet the requirement for every vehicle, but the entire fleet in each category must average it.

The manufacturers argue the standards force them to build smaller cars that don’t stand up as well in a crash and that consumers don’t want to buy.

“Make no mistake, the Senate proposals would eliminate SUVs, minivans and pickup trucks,” said Gloria Bergquist, spokeswoman for the Alliance of Automobile Manufacturers. “If these proposals pass, the only place you’ll see a light truck is in a museum.”

But proponents of increased fuel economy say it is necessary to reduce dependence on foreign oil and cut greenhouse gas emissions.

“This is a critical issue for our energy and American security,” Kerry said.

The Bush administration is studying the impact of increasing fuel economy on automobile safety and aims to set its own standards. Meanwhile, White House officials have been meeting with Senate Republicans and key GOP aides to block any legislated standard.

The senators’ staffers are trying to work out differences in Republican and Democratic plans.

Senate Majority Leader Tom Daschle hopes to include the compromise when he introduces his energy plan Tuesday.