Obama is off to Asia to boost trade, cooperation

The deal faces strong opposition from the leading 2016 presidential candidates and other critics, who say it doesn't do enough to protect U.S. workers from unfair competition.

Five Republican senators sent the president a letter Friday labeling Vietnam "one of the most repressive regimes in the world" and urging Obama to press Vietnamese leaders to do more to respect freedom of religion and expression and other human rights.

Before Obama left, Vietnam granted early release from prison to a Catholic priest who is one of its most prominent dissidents.

Ly, 70, has served several long terms in prison or under house arrest for promoting political and religious freedoms in the communist nation.