A Mexican man convicted of murder has been executed in Texas, in a case that has drawn international attention and strained relations between the United States and Mexico.

Suarez was 19 when he killed the undercover police officer

Javier Suarez Medina, 33, died by lethal injection on Wednesday, after spending 13 years on death row.

He was executed despite personal appeals by Mexican President Vicente Fox for his life to be spared.

Suarez was convicted in 1989 for the killing of a police officer who was working undercover in Dallas as a drug trafficker.

Suarez, who was 19 at the time of the crime, admitted to the murder - but said he did not know the victim was a police officer.

Intervention

The Mexican authorities had argued Suarez's rights were violated because police failed to tell him he was entitled to legal assistance from the Mexican consulate.

Mexican foreign ministers say Suarez was not told he qualified for assistance

"The Mexican Government was prevented from providing priority assistance that might have influenced the outcome of his trial," President Fox said in a letter to Texas Governor Rick Perry on Monday.

On Wednesday Mr Fox spoke by telephone with US President George W. Bush, in a last-ditch attempt to secure a stay of execution.

Suarez was born in Mexico, but has lived in Texas since the age of three. Mexico said that under the Vienna Convention, the US authorities were required to put him in contact with Mexican officials.

Dallas police have said they did not know he was Mexican.

Finding religion

Mexico and 13 Latin American and European nations supported an unsuccessful appeal to the US Supreme Court.

UN High Commissioner for Human Rights Mary Robinson also sent a letter to Secretary of State Colin Powell calling for clemency.

She said there were "serious concerns that the trial proceedings in the case had not complied with international human rights standards."

Suarez became religious in prison, and recently told reporters he preferred to die than continue to live in the intense isolation of death row.