By Kristina Peterson

WASHINGTON -- House Speaker Nancy Pelosi said Tuesday night she had reached an agreement with Treasury Secretary Steven Mnuchin to add farm aid and food assistance to a spending bill needed to prevent a partial government shutdown next month.

The bipartisan agreement is expected to smooth passage of the stopgap measure, which would keep the government running through Dec. 11 and avoid a partial shutdown when the government's current funding expires next Thursday.

The agreement between Mrs. Pelosi (D., Calif.) and Mr. Mnuchin would add to the spending bill $21 billion sought by the White House for the Commodity Credit Corp., or CCC, a Depression-era program designed to stabilize farm incomes that permits borrowing as much as $30 billion from the Treasury to finance its activities. The agreement prohibits any payments from going to fossil fuel refiners and importers, a concern of Democrats.

President Trump has tapped the CCC program to finance both trade relief and coronavirus-related aid for farmers, a second round of which he announced at a campaign rally in Wisconsin last week. But the program has traditionally been used to send out payments established under bipartisan farm bills, some of which the Agriculture Department had said could be subject to delays as soon as October.

Mrs. Pelosi and Mr. Mnuchin also agreed to add $8 billion in nutrition assistance, the speaker said. That includes a one-year extension of a program expiring at month's end that would provide funding to families of school-age children to buy groceries, replacing the free or reduced-price meals they would have received at school.

"We have reached an agreement with Republicans ... to add nearly $8 billion in desperately needed nutrition assistance for hungry schoolchildren and families," Mrs. Pelosi said in a statement. "We also increase accountability in the Commodity Credit Corporation, preventing funds for farmers from being misused for a Big Oil bailout."

The House was expected to vote on the bill later Tuesday night.

Write to Kristina Peterson at kristina.peterson@wsj.com