MEXICO CITY — Confronting a Mexican drug war that is "sowing chaos in our communities," President Obama signaled yesterday he will not seek renewal of a U.S. assault weapons ban but instead will step up enforcement of laws banning the transfer of such guns across the border.

Obama had pledged during his campaign to seek renewal of the ban but has bowed to the reality that such a move would be unpopular in politically key U.S. states and among Republicans as well as some conservative Democrats.

Obama met with Mexican President Felipe Calderon, who has been conducting an aggressive fight against drug cartels and had hoped to persuade Obama to push for reinstatement of the gun ban. Obama arrived here on the first stop of a trip that will take him to a weekend Summit of the Americas in Trinidad, bringing together the leaders of 34 Western Hemisphere democracies.

Allies in the fight against drugs, Obama and Calderon took different stands on U.S. sanctions against Cuba. Calderon said the 47-year-old U.S. trade embargo has not been successful in forcing Cuba to adopt democratic reforms.

"I share fully the idea we do not believe that the embargo or the isolation of Cuba is a good measure for things to change in Cuba," Calderon said.

Obama pointed to the announcement this week that the U.S. was softening sanctions, allowing Americans to make unlimited transfers of money and visits to relatives in Cuba. But he said Cuba needs to reciprocate with actions that are "grounded in respect for human rights."

Cuban President Raul Castro, attending meetings in Venezuela, said his government is willing to discuss "everything" with Washington — including human rights, political prisoners and freedom of the press — as long as the discussion is "on equal terms."

Obama acknowledged that the United States shares responsibility for bloodshed and kidnappings in Mexico that have spilled into the United States. He said the U.S. must crack down on domestic drug use and the flow of weapons into Mexico.

Obama also said the United States and Mexico must work together to stem the problem of illegal immigration. He said he favors a more orderly process for immigrants who want to come to the United States and a pathway to legalization for those already in the U.S. illegally.

"My country has been greatly enriched by immigrants from Mexico," he said.

The two leaders also pledged to cooperate on combating global warming and the global recession.