US President George W Bush has returned to Washington after visiting Panama on a last stop of his Latin American tour.
Modernising the Panama Canal is in US interests, says President Bush
While in Panama, he backed plans to widen the canal and said the two countries were close to a trade deal.
His visit to Panama was seen by correspondents as a respite after tense talks during the weekend.
At the Summit of the Americas in Argentina, several leaders balked at Mr Bush's appeal for a quick agreement on a regional free-trade area.
Mr Bush wrapped up his trip with a visit to the 50-mile (80km) Panama Canal, which was opened by the US in 1914 and handed over to Panama in 1999.
He called for the canal to be modernised to allow access to more shipping, but did not say if the US would help towards the estimated $10bn (£5.7bn) cost.
At a joint press conference with Panamanian President Martin Torrijos, he also said the two nations were "close to coming to an agreement" on trade.
But he said it would need to be approved by the US Congress.
The US reached a free-trade deal last year with other Central America countries and the Dominican Republic.
During his visit to Brazil on Sunday, Mr Bush faced calls to eliminate US agricultural subsidies.
He promised his Brazilian counterpart, Luiz Inacio Lula da Silva, to work towards that aim, which he said was fundamental in order to move towards free trade around the world.
But he also accused some Latin American nations of rolling back the democratic progress of the last 20 years - in an apparent swipe at Venezuelan President Hugo Chavez.
Mr Bush had avoided talking about President Chavez at the summit of the Americas, despite inflamed speeches from the Venezuelan leader blaming US interference for Latin America's ills.
But he gave his vision for the economic and democratic development of the Americas in a speech later on Sunday to political and business leaders in Brasilia.