(Recasts, updates with lawmakers looking at farm law without new funds)

By Charles Abbott

WASHINGTON, March 12 (Reuters) - The new U.S. farm law may shortchange programs from food stamps to land stewardship and crop supports by billions of dollars because Congressional leaders have not come across with a promised $10 billion increase, farm committee leaders warned on Wednesday.

"We have to have a plan in place that is workable," said the House chairman, Collin Peterson, after four House and Senate Agriculture Committee leaders met for an hour in the Capitol. The funding gap was a key topic.

Democratic leaders in Congress decided on Feb. 26 to seek a $10 billion increase over 10 years for the new law. But there is no agreement yet on funding and time is running out to enact a new law, nearly six months overdue. The funding level will be decided by the House and Senate tax committees.

The agriculture leaders said they were looking at a "baseline" bill with no new funding as a fallback. "That's certainly something that has to be considered," said Virginia Rep. Bob Goodlatte, the Republican leader on the House Agriculture Committee.

A baseline bill would mean billions of dollars less than now proposed for public nutrition, land stewardship, biofuels and specialty crop programs. Proponents say a farm bill cannot pass Congress unless it spends more on those popular programs. It was unclear how money would be allocated in a baseline bill for crop supports, nutrition or other programs.

Senate Agriculture Committee chairman Tom Harkin, Iowa Democrat, said money could be shifted within the bill so popular programs got increases from current levels but they would not be as large as proposed in House and Senate farm bills passed last year.

The omnibus farm bill would oversee about $600 billion over 10 years with two-thirds of it going to public nutrition. Farm bills cover crop supports, nutrition, exports, stewardship, agricultural research, biofuels and rural development.