By Charles Abbott

WASHINGTON (Reuters) - Congressional negotiators agreed on a $10 billion increase for nutrition programs including food stamps under the new U.S. farm law, up $500 million from the earlier target, the heads of the Senate and House Agriculture Committees said Thursday.

Senate Agriculture chairman Tom Harkin, a Democrat from Iowa, disclosed the $10 billion figure during a brief Senate debate over a bill to keep current agricultural programs running until May 2 while House and Senate negotiators finish work on the $600 billion farm law.

His House counterpart, Minnesota Democrat Collin Peterson, confirmed the figure to reporters in the Capitol.

Senators passed the one-week extension of the current law on a voice vote. The House concurred in a voice vote at midday, sending the bill to the White House.

The Bush administration was expected to accept the extension. The farm bill is six months past due.

"We are very close to getting this agreement done," said Harkin, adding that negotiators may wrap up work by the middle of next week.

Negotiators deadlocked for weeks over how to pay for a $10 billion spending increase for the farm law, and over Senate insistence on including a tax package in the bill.

The package of tax cuts began as $7.5 billion and has been whittled to $1.4 billion to $1.6 billion, Harkin said in a teleconference with Iowa reporters.

"That is not the end of the story," said Senate Budget Committee Chairman Kent Conrad, a North Dakota Democrat, suggesting increases were possible. "There are things that have been bucked to the leadership level."

House and Senate negotiators have agreed on a farm-bill framework that puts more money into nutrition, land stewardship, specialty crops and biofuel development while cutting crop insurance, crop subsidies and agricultural research.

An additional $730 million must be cut from crop supports, said Peterson.

Senate Finance Committee chairman Max Baucus, a Montana Democrat, mentioned half a dozen issues still at play.

They include a 6-cent a gallon cut in the ethanol tax credit, a Senate proposal for a disaster relief fund for agriculture, faster tax write-offs for owners of race horses and tax incentives for timber companies.

Baucus and Conrad said the administration opposed a securities reporting proposal that negotiators would use to provide $6 billion of the offsets needed for the farm bill.

There are suggestions among negotiators to cut the "direct" payments that guarantee $5.2 billion a year to cotton, grain and soybean growers regardless of market conditions.

Sen. Larry Craig, a Republican from Idaho, blocked Harkin from amending the bill into a two-week extension. The winter wheat crop will be ready for harvest soon, he said, and growers do not know what federal supports will be offered.

"It is time Congress senses urgency" to pass an omnibus farm law, Craig said.

(Reporting by Charles Abbott; Editing by John Picinich)