Secretary of State Hillary Rodham Clinton promised Wednesday that the U.S. government would spend nearly $300 million this year helping governments in Central America confront the mafias that smuggle cocaine to American consumers.

“The United States will back you,” she said at a regional summit here. “We know demand for drugs rests mostly in my own country.”

On a visit to El Salvador in March, President Obama said the United States would give $200 million to fight the street gangs and drug traffickers that have left the region with the highest homicide rates in the world.

The increase announced by Clinton represents repackaging of money dedicated to other programs as well as heightened concern among U.S. officials that the fragile democracies of Central America are struggling with surging criminality fueled by the movement of drugs north and weapons south.

“We know the statistics — the murder rates surpassing civil war levels,” Clinton said in a reference to the Cold War-era conflicts that consumed Guatemala, Nicaragua and El Salvador in the 1980s and 1990s. “We know the wave of violence also threatens our own country.”

Leaders called the two-day summit historic, as Central American nations put aside longtime rivalries to devise a regional plan to bolster security that includes professionalizing the police forces, training judges, reforming corrupt prison systems, sharing intelligence and equipment, and trying to divert poor young people away from lives of crime.

The seven countries of Central America have proposed 22 projects, which would cost about $900 million, and the leaders stressed in their remarks Wednesday that they do not have the money to do it alone.

“For us, it is the difference between life and death,” said Guatemalan President Alvaro Colom. He said the United States and other “consumer countries” in Europe owe support to “transit countries.”

Colom said that Central America spends $4 billion in security-related costs but that last year, despite pledges of almost $1 billion from the United States, Europe, the World Bank and other donors, only $140 million in aid was delivered.

Luis Alberto Moreno, president of the Inter-American Development Bank, said the fund will spend $500 million over the next two years supporting the Central American plan. “They are working together, in a serious way — this is an important part of the story,” Moreno said in an interview.

Mexican President Felipe Calderon said, “What would happen if Mexico or Central America were to the north of the United States? We would not be sitting here today.”

Calderon called the trafficking route for cocaine from South America to the U.S. border “a highway of death” and U.S. arms manufacturers “an industry of greed.” He said consumer countries should give the same amount of money to transit countries that the drug cartels make from their illegal trade — about $35 billion a year.

Clinton, however, said the private sector in Central America should contribute more. “The businesses and the rich in each country must pay their fair share of taxes,” she said. The region has some of the lowest rates of tax payments in the world.

Colombian President Juan Manuel Santos told his Central American counterparts not to lose heart. “Drug trafficking brought our country to its knees,” he said. “But we stood back up.”

Santos said his government seized 40,000 weapons last year, which included “powerful, sophisticated arms” that arrived via Fed Ex. “They took them apart and sent the pieces separately,” he said. “Where did they come from? The United States.”

President Mauricio Funes of El Salvador said the Zetas crime mafia is trying to bribe elite police units in his country with $5,000 monthly payments to steal guns and grenades from the armed forces.

Honduran President Porfirio Lobo said, “Our democracies have never been so vulnerable,” adding that in his country, gang members outnumber police officers and soldiers.