In the first visit to Mexico by an American president in 12 years, Barack Obama praised the nation's leadership for its efforts in fighting drug rings.

Obama, who promised Mexicans improved relations with the country during a stop there on Thursday, said Mexico's president had done a "heroic and outstanding job" in fighting organized drug-trafficking.

He also called Washington's policies "a shared responsibility" in preventing international drug cartels from proliferating.

His praise came just hours after 16 people were killed in a clash between government soldiers and drug men in southwest Mexico, but Obama was not discouraged.

He heads to the islands of Trinidad and Tobago today where a 34-nation Summit of the Americas will be held.

Obama is expected to receive a warm reception from the islanders, who supported him during his presidential run.