President Barack Obama will press Congress to release more than $100m (£60m) of aid to help Mexico in its war against the drug cartels.
The funds have been held up by complaints on Capitol Hill that the Mexican army has committed human rights abuses in its struggle to destroy the drug barons and end the violence that has killed an estimated 11,000 people in the country.
The issue was one of several bones of contention at yesterday's summit between the leaders of the US, Canada and Mexico in Guadalajara, now an annual fixture aimed at building on the ties established through Nafta, the North American Free Trade Agreement that came into effect in 1994.
Mexican officials have repeatedly pushed for the money to be released, insisting that reports of abuses by the army have been exaggerated, and at a private meeting here with his opposite number Felipe Calderon, Mr Obama reiterated his support for the Mexican government's offensive.
Likewise, at a press conference yesterday he commended the Mexican government for its "courage in taking on the drug cartels" and pledged to "remain a full partner in that effort."
But the money has not been forthcoming, despite the administration's best efforts, including Mr Obama's acknowledgement that the US shared responsibility for the crisis given its demand for drugs and its role as a de facto supplier of the guns that arm the militias operated by the cartels.
The drugs issue is one of several that was unlikely to be resolved by the talks between Mr Obama, Mr Calderon and Stephen Harper, the Canadian Prime Minister, at a summit that lasted a mere 20 hours.
Their personal relations may be excellent, to the point they have been dubbed the "Three Amigos", but the problems confronting the leaders are sensitive and, if anything, have been intensified by the global economic crisis.
They include a row over the cancellation by Congress of a Nafta provision allowing Mexican trucks to operate in the US, and the Buy American provisions that formed part of Mr Obama's $780bn stimulus package, to which Canada and Mexico have objected.
The immigration issue is also unresolved. After the Bush administration failed to push through changes, Mr Obama has said that he wants a bill to straighten out the status of millions of illegal immigrants in the US, many of whom are from Mexico, but it will have to wait its turn behind the his top priorities of reforming the US health care and energy sectors.
The three countries did however agree to step up co-operation on swine flu, which first broke out in Mexico. After a summer lull, the H1N1 virus is predicted to return with a vengeance to the northern hemisphere during the autumn. Public health officials are readying medicines and public education campaigns, hoping to curb the spread of the virus without disrupting trade and tourism.
"We're going to do everything possible to minimise the impact," John Brennan, one of Mr Obama's top homeland security advisers, said.