WASHINGTON (Reuters) -The Trump administration is expected to announce a plan as soon as Tuesday to bail out U.S. farmers stung by trade disputes and big harvests, with the initial outlay potentially totaling up to $15 billion, according to sources familiar with the matter.

The plan, however, could be difficult to roll out as an ongoing government shutdown prevents the kind of Congressional action needed to approve such a large payout, and existing government reserves fall short, the sources said.

Farmers generally support President Donald Trump but have pressed his administration for trade deals as China continues to spurn U.S. soybean purchases amid tit-for-tat tariffs, and a record corn harvest threatens to sink farmer profits.

Republican lawmakers have warned farmers face "financial calamity" if they do not receive aid by the end of the year. Treasury Secretary Scott Bessent said last week that the White House would announce aid for farmers on Tuesday.

Three sources told Reuters they expected the administration to announce the package this week.

One of those sources said the bailout would total somewhere between $10 billion and $15 billion, and would be a necessary bridge to get farmers through the harvest months and could be followed by additional aid.

The funds would go to soybean farmers affected by the China trade spat, as well as other types of commodity farmers, though the exact details were not yet determined, that source said.

A U.S. Department of Agriculture spokesperson said farmers are benefiting from lower taxes, trade deals and updates to farm programs included in Trump's July tax-cut and spending bill. 

"President Trump has made it clear he will not leave farmers behind, so USDA will continue to assess the farm economy and explore the need for further assistance, however, there is nothing new to share at this time," the spokesperson said.

National Economic Council Director Kevin Hassett on Monday said the White House had held several meetings on farmer aid in the past two weeks.

"We're taking big measures and those big measures are going to be public really, really soon," he said on CNBC. 

SHUTDOWN COMPLICATES AID PLAN    

Trump has said repeatedly that the administration will use tariff income to pay for farmer aid. But such direct payments to farmers are statutorily capped at $350 million, a fraction of the sum being discussed, and can only be adjusted by Congress. 

That adjustment is difficult to achieve while the federal government is shut down, two of the sources said.

Another option is to draw down funds from the Commodity Credit Corporation, a financing mechanism at the USDA that is typically refilled each year in autumn, but has not been refilled because of the shutdown, said Jonathan Coppess, associate professor at the University of Illinois Urbana-Champaign.

During Trump's first term, he used the CCC to pay farmers more than $23 billion in trade aid, about a $3 billion overpayment, according to the Government Accountability Office.

The remaining funds currently in the CCC are likely insufficient to pay for the package being discussed, Coppess said. 

Farmers are already set to receive near-record government payments of more than $40 billion this year, fueled by disaster and economic aid passed by Congress last year.