Obama heads for Less Friendly 'Three Amigos' Summit

President Barack Obama headed south Wednesday for a North American leaders' summit marked by frictions between the "three amigos" of Mexico, Canada and the United States.

President Enrique Pena Nieto will host Obama and Canadian Prime Minister Stephen Harper at the ornate state government palace in Toluca, near Mexico City, for the day of talks.

The partners of the 20-year-old North American Free Trade Agreement (NAFTA) are locked in several thorny disputes likely to surface in the talks and at a joint news conference at day's end.

More than 5,000 soldiers and police officers patrolled city streets lined with metal fences, while the leftist opposition planned to hold a protest near the venue.

Pena Nieto has sought to turn attention away from Mexico's security problems, which have left more than 77,000 people dead in a seven-year-old drug conflict, and towards trade and his sweeping economic and energy reforms.

Although the allies want to find ways to improve NAFTA, their talks come with some discord on other issues.

Obama will no doubt face a new entreaty from Harper to quickly make up his mind on the Keystone XL pipeline project, which would carry crude from Canada's oil sands across the continental United States to Texas.

Canada is deeply frustrated at delays in the project, which is awaiting a construction permit and has caught Obama's administration between its backers in the environmental community and claims it will create thousands of jobs.

But Harper is unlikely to get an answer, as Secretary of State John Kerry continues his deliberations on whether to give the project the go-ahead.

"What President Obama will do is explain to (Harper) where we are in the review ... and indicate that we'll of course let our Canadian friends know when we've arrived at a decision," said a senior U.S. official on condition of anonymity.

A State Department report last month concluded that the pipeline would not significantly impact global warming, as Canada would extract the dirty tar sands oil even if it is not built.

Pena Nieto will, meanwhile, likely offer Obama some support, but also a measure of frustration over the failure to pass comprehensive immigration reform in the United States.

The U.S. president made the issue a centerpiece of his agenda but has seen his hopes of enacting a law to bring more than 11 million illegal immigrants, many of them of Mexican origin, out of the shadows repeatedly frustrated by Republicans.

Pena Nieto's government has also been investigating claims sourced to documents leaked by fugitive U.S. contractor Edward Snowden that U.S. National Security Agency (NSA) eavesdropping programs targeted his communications and those of two predecessors.

Mexico and Canada have their own dispute over tough visa requirements that were imposed by Ottawa on Mexican travelers in 2009 to curb an influx of refugee applications.

Pena Nieto called on Harper after a bilateral meeting in Mexico City on Tuesday to negotiate a solution to eliminate the visas "in a near future."

Officials want to put the focus on improving NAFTA, but they say the deal will not be reopened despite bottlenecks that are slowing truck movements at the U.S.-Mexico border.

Officials say NAFTA can be revitalized via the 12-nation Trans-Pacific Partnership (TPP) trade pact that Washington is hoping to conclude this year.

But Obama's partners will be keen to know how he plans to overcome opposition from fellow Democrats to the deal in a mid-term election year, as well as his hopes of securing "fast-track" powers to swiftly conclude the deal.

Despite the niggling frictions, U.S. officials are in no doubt of the value of close relations with their closest neighbors.

A third of U.S. exports go to Mexico and Canada and the trade supports 14 million jobs on U.S. soil, U.S. officials say.