WASHINGTON (Reuters) - The United States expects only "incremental" progress on longstanding farm trade issues in high-level talks with China on Wednesday, U.S. Agriculture Secretary Tom Vilsack said.

"Hopefully we'll be able to get some progress, but it's incremental. It's slow but sure," Vilsack told reporters after a speech at the U.S. Chamber of Commerce.

(Reporting by Doug Palmer; Editing by Vicki Allen)