WASHINGTON -- Republican leaders of the House and the Senate gave senior lawmakers negotiating energy legislation until mid October to reach a deal or face the prospect of an attempt by the leadership settle the remaining issues, lawmakers and aides said recently.

After a private session recently convened by Senator Bill Frist, Republican of Tennessee, who is the majority leader, and Speaker J. Dennis Hastert, Republican of Illinois, participants said no breakthrough was reached but that the principal lawmakers were put on notice that Congress would not adjourn this year until an energy bill was finished.

The measure gained new prominence after the August blackout, and coming to an agreement that can withstand opposition in the Senate will not be easy. "It's a pretty tenuous situation," said Senator Charles E. Grassley, Republican of Iowa and a chief author of the tax incentives in the energy bill.

At issue are gasoline additives, payment for transmission line improvements and subsidies for a natural gas pipeline in Alaska. Lawmakers said the goal was to present a final proposal to a joint House-Senate negotiating committee in mid October.

Top Senate aides said apparent resolutions were becoming evident on some critical issues. One said it was now a foregone conclusion that the final proposal would not include oil drilling in the Arctic National Wildlife Refuge because enough Senate Democrats and Republicans have indicated they would block the bill if it included the drilling provision.

On another contentious issue, a senior aide said Senate Republicans were prepared to accept a proposal that phases out production of the gasoline additive methyl tertiary butyl ether in exchange for giving limited liability protection to producers of the substance, which is blamed for groundwater contamination. That approach has drawn a filibuster threat from Democrats and is opposed by local government officials who say it would leave states and municipalities responsible for cleanup costs. Forty-three senators this week signed a letter protesting plans to grant the companies immunity.