President Obama on Thursday appeared to reject the idea of arming U.S. agents in Mexico, saying after a meeting with Mexican President Felipe Calderon that the two governments will look at other ways to protect American officials in the wake of a fatal shooting last month.

"There are laws in place in Mexico that say that our agents should not be armed," Obama said, describing the U.S. role south of the border as an "advisory" one. "We do not carry out law enforcement activities inside of Mexico."

The president's statement answers speculation about how far the administration would go in reforming safety measures in response to the killing three weeks ago of Immigration and Customs Enforcement agent Jaime Zapata in Mexico. The shooting death raised questions in the U.S. about Mexico's ability to control violence but U.S. officials earlier wouldn't say whether Obama would press the Mexican leader to allow U.S. agents to be armed.

Coming out of the meeting Thursday afternoon, both presidents stressed that U.S. agents cannot be armed. Obama said he was nevertheless concerned about the safety of agents and that they would examine "procedures and protocols" for how to better protect them.

Calderon said Mexican officials are "deeply analyzing alternatives."

Obama, signaling the two presidents discussed the killing, thanked the Mexican government Thursday for its cooperation in the investigation and vowed that the United States would be a "full partner" in fighting the drug cartels.

"Whether they live in Texas or Tijuana, our people have a right to be safe in their communities," Obama said. 

Shortly before the meeting, U.S. Homeland Security Secretary Janet Napolitano also told a House committee that the administration would seek to extradite the suspects in the case so they can be prosecuted in the United States.

Several suspects have been arrested in the killing of Zapata, and Mexican authorities say one has confessed. Napolitano declined to discuss reported statements from suspects being held in Mexico that the Feb. 15 killing was a case of mistaken identity

Despite the ongoing concerns about the ICE agent killing, the president was able to announce a breakthrough in a longstanding trucking dispute between the two countries.

Obama, speaking at a joint press conference with his Mexican counterpart, announced that the countries had "finally found a clear path" to resolving the trucking dispute, saying the proposal would lift tariffs on U.S. goods, expand U.S. exports and create jobs.

The plan would open up U.S. highways to Mexican trucks, removing a long-standing roadblock to improved relations between the North American allies. An Obama administration official said the two leaders have agreed to a phased-in plan that would authorize both Mexican and U.S. long-haul carriers to engage in cross-border operations, provided that the Mexican trucks meet U.S. safety standards. Both countries were given this authority under the 1994 North American Free Trade Agreement, but the U.S. has refused to allow Mexican trucks access amid concerns over their ability to meet America's stringent safety and environmental standards.

At the press briefing Thursday, Obama also re-emphasized his commitment to pursuing comprehensive immigration reform, something that has eluded him so far.

The contentious debate over immigration dominated Calderon's visit to the White House in May, shortly after Arizona passed a law that makes it a state crime to be in the U.S. illegally and requires police to question people about their immigration status if there's reason to suspect they're illegal. Mexico's government strongly opposes the law, and the Mexican Senate this week urged Calderon to again vehemently make their opposition known to Obama.

Congressional Hispanic Caucus Chairman Rep. Charles Gonzalez, D-Texas, said in a statement Thursday that his group remains "committed" to comprehensive immigration reform, despite the failure last year to pass a bill providing some illegal immigrant students and military members a pathway to legalized status. "Despite this impasse, the CHC remains committed to our stated goal of passing comprehensive immigration reform and will continue to work to find a bipartisan solution to one of our nation's most untenable problems," Gonzalez said.

Obama and Calderon were also expected to discuss U.S. aid to help support Mexico in the drug war, something Obama touched on at the press briefing. A senior administration official said the U.S. plans to speed up implementation of the $1.4 billion Merida Initiative, with $900 million to be doled out by the end of the year. The official spoke on the condition of anonymity in order to preview the announcement.

The announcement comes as the State Department issued a report praising Mexico's government for increased drug seizures and better efforts to combat narcotics trafficking and money laundering. But it said Mexican production of marijuana, heroin and methamphetamines was rapidly rising, and that cartels were becoming even more dangerous through use of sniper rifles, grenades and increasingly military tactics.

The Associated Press contributed to this report.