Washington (CNN) -- President Barack Obama and the visiting leaders of Mexico and Canada on Monday pledged joint efforts to combat drug cartels in Mexico and expand international trade, including support for Canada and Mexico joining the Trans-Pacific Partnership.
Citing the increasingly global nature of issues such as trade and security, the three leaders told reporters that what happens within the borders of their neighboring countries affects everyone in North America.
Obama repeated his previous support to reduce the demand for drugs in North America and slow the flow of guns and money across the border into Mexico.
Mexican President Felipe Calderon expressed appreciation for such efforts but also sounded frustrated with the continuing availability of weapons including assault rifles.
In particular, he said the expiration of the U.S. assault weapons ban in 2004 "coincided almost exactly with the beginning of the harshest period of violence we've ever seen ... during my government."
"We have seized over 140,000 weapons in four years and I think that the vast majority have been assault weapons ... and many, the vast majority of these weapons were sold in gun shops in the United States along the border of the U.S. and Mexico," Calderon said. "There are approximately 8,000 weapons shops. If we do our accounts, that means that there's approximately nine weapon stores for each Walmart that exists in the United States and Mexico."
Monday's North American Leaders' Summit was the first such meeting in more than two years and served as a prelude to the Summit of the Americas set for mid-April in Cartagena, Colombia.
The three leaders met in the morning and had a working lunch before holding a joint news conference in the White House Rose Garden.
The talks came less than a week after the three nations' defense ministers met in Canada, pledging to do more to confront and combat drug cartels on the continent.
Military officials said they would dedicate more time to patrolling waters and inspecting shipping containers that cross borders. They also said they were working to share more intelligence in a timely manner.
Obama said Monday that the United States and Canada must be concerned about the powerful Mexican drug cartels because they influenced security throughout the region, including Central America.
"When you have innocent families and women and children who are being gunned down on the streets, that should be everybody's problem, not just our problem, not just their problem," Obama said. "There is a sense of neighborly regard and concern that has to be part of our calculus and our foreign policy."
Allowing the drug cartels to expand their power and influence would pose an even greater threat to the region and "could have a deteriorating effect overall on the nature of our relationship," Obama said.
In February, Calderon called called on U.S. officials to stop gun trafficking across the border, saying the move would be the best thing Americans could do to stop brutal drug violence.
"If we don't have mechanisms to forbid the sale of weapons ... then we are never going to be able to stop with the violence in Mexico or stop a future turning of those guns upon the U.S.," Calderon said Monday.
"Thinking that what happens in Mexico doesn't have anything to do with the security of the citizens of this country or of any other citizen of North America is a mistake," he added later. "We have to understand that we are all tied to one another."
The three leaders also expressed support for streamlining regulations and taking other steps to increase trade among themselves and with the rest of the world.
Obama said the United States welcomed the desire by Canada and Mexico to become members of the Trans-Pacific Partnership, a planned free trade agreement comprising the United States, Australia, Chile, Malaysia, New Zealand, Peru, Singapore, Vietnam and Brunei.
He noted that any trade negotiation involved participants having to make adjustments and concessions, but called such give-and-take part of the normal process and said he didn't see any extraordinary issues emerging.
Canadian Prime Minister Stephen Harper said joining the Trans-Pacific Partnership was a "logical extension" of what he called Canada's ambitious trade agenda, while Calderon added Mexico could add a lot to the planned partnership.
In a joint statement after the talks, the three leaders also announced plans for greater cooperation on climate change issues as well as the North American Plan for Animal and Pandemic Influenza, which they said would "strengthen our response to future animal and pandemic influenza events in North America."
There was no mention in their statement or remarks to reporters of the proposed Keystone XL oil pipeline from Canada's tar sands production to the U.S. Gulf Coast.
The Obama administration blocked the project this year, blaming political wrangling, and Harper has made clear that Canada would seek other export destinations for the tar sands oil if no progress occurs.
Last year, officials postponed a previously scheduled meeting of the three leaders after Mexico's interior minister, Francisco Blake Mora, died in a helicopter crash. Calderon hosted the last North American Leaders' Summit in Guadalajara, Mexico, in 2009.
The North American leaders, nicknamed by some as the "three amigos," face differing political futures. Calderon will step down later this year because of term limits in Mexico, while Harper led his Conservative Party to victory last May and Obama faces a re-election challenge in November.
CNN's Paula Newton and Catherine Shoichet contributed to this report.