WASHINGTON  Seeking to ease the tensions that had put a chill in this country’s relations with Mexico, President Obama on Thursday heaped praise on President Felipe Calderón’s campaign against the drug-trafficking organizations wreaking havoc south of the border.

He also announced a breakthrough on a festering trade dispute that prevents Mexican trucks from operating on American highways.

At a joint news conference at the White House with Mr. Calderón, Mr. Obama said Mexico had shown “extraordinary courage,” in its stand against a wave of crime and violence that has left tens of thousands of Mexicans dead since 2006, threatening the stability of a country whose democracy is barely a decade old.

And he pledged that the United States, which provides a market for the illegal drugs, would do more to help.