US President Barack Obama has come under fire from Asia-Pacific leaders for backsliding on free trade at a regional summit in Singapore.

Mexican President Felipe Calderon complained about US foot-dragging on full implementation of the North American Free Trade Agreement (NAFTA).

NAFTA, which entered into force in 1994, was supposed to remove most barriers to investment for member states Mexico, Canada, and the United States.

"President Obama is facing severe political constraints that run counter to free trade," Calderon told the Asia-Pacific Economic Cooperation (APEC) Forum on Saturday.

Russian President Dmitry Medvedev made the same point and singled out Washington for "going in the opposite sense of free trade."

Chinese President Hu Jintao said curbing protectionism in international trade would help revive the world economy.

The US is accused of protectionism and lack of openness in international trade since the economic downturn began last year.

Even the US Congress has turned sour on free trade since the onset of the worst economic crisis since World War II.

Obama arrived in Singapore on Saturday to join the 20 other APEC leaders after a visit to Tokyo.

JR/SS/HGL