President Obama unveiled plans Thursday to double U.S. exports over the next five years in hopes of spurring job growth, an ambitious goal that may rekindle the battle over free-trade policy.

The president acknowledged the formidable barriers to his goal: doubts in Congress over new free-trade agreements, misaligned currencies that make Chinese products cheaper on global markets, and continued weakness in global demand, all problems that could dwarf efforts to promote U.S. products and services abroad.