The United States’ top trade negotiator was in Iowa last week to rally support for the Trans-Pacific Partnership (TPP), a wide-ranging trade pact that is projected to boost farm income by $4.4 billion annually.

But time is running short for Congress to pass TPP, U.S. Trade Representative Michael Froman said in a meeting with Iowa farmers and agriculture leaders last week in Des Moines.

"We’ve got to get it done this year," he said. "If we don’t get it done this year, given the current political climate, I’m not sure when it would get done."

TPP is...