Congress moved Thursday to prevent the Internal Revenue Service from cutting operating hours for toll-free telephone help lines next year.

The effort to block the reductions marked the latest step in a yearlong disagreement between Congress and the IRS over taxpayer service.

Agency Commissioner Mark Everson has been looking for places to trim spending and absorb reductions in the agency's customer service budget.

He planned to shave three hours off the daily telephone operating hours, for a savings of about $10 million, beginning Jan. 23. The change would have reduced daily operations from 15 hours to 12 hours a day.

IRS statistics show that about 93 percent of telephone calls come during the new service hours, between 8 a.m. and 8 p.m., local time.

Lawmakers inserted language prohibiting the IRS from reducing its telephone operating hours into a bill funding the Pentagon, one of the last expected to reach the president's desk this year. The Senate passed the bill Wednesday, and the House was expected to pass it Thursday.

"We're studying the language in the bill," said an IRS spokesman.

Congress tussled with the IRS earlier this year after Everson revealed plans to close 68 of the agency's 400 taxpayer assistance centers, where taxpayers can get face-to-face help with tax problems. Lawmakers blocked that plan.

They further instructed the IRS, through the bill funding the tax agency for the current fiscal year, not to reduce taxpayer services without first asking Treasury Department auditors to study the changes and submitting the report to lawmakers who control the agency's budget.