HOUSTON — A Mexican national facing execution in Texas this week has drawn support from Mexican officials, a former Texas governor and U.S. Secretary of State John F. Kerry, who appealed to Gov. Rick Perry and state courts for a reprieve — so far, unsuccessfully.

Edgar Tamayo, 46, a Mexican citizen, is scheduled to be put to death Wednesday for fatally shooting Houston Police Officer Guy Gaddis in 1994.

Gaddis, 24, had been flagged down near a nightclub by a man who accused Tamayo of robbing him. The officer arrested Tamayo, handcuffed him and put him in the back of his patrol car. The officer was driving away when Tamayo drew a pistol he had concealed and shot Gaddis three times in the back of the head.

Tamayo’s attorneys have appeals pending. A hearing has been scheduled for Tuesday morning in the U.S. District Court for the Western District of Texas in Austin to consider their challenges to the state clemency process.

On Sunday, Mexico’s foreign ministry released a statement objecting to the execution.

"If Edgar Tamayo's execution were to go ahead without his trial being reviewed and his sentence reconsidered ... it would be a clear violation of the United States' international obligations," the statement said in Spanish.  "The Mexican government opposes the death penalty and is determined to use all available recourses to protect those nationals in danger of receiving such a sentence.”

The 32 states with capital punishment have executed 28 foreign nationals since 1976, according to the Washington, D.C.-based Death Penalty Information Center, which opposes capital punishment.

“Mexico typically intervenes in these cases, capital cases, even before the trials occur so they often don’t result in a death sentence anymore. It might well have made a difference in Tamayo’s case,” said the center’s executive director, Richard Dieter.

Tamayo, a laborer from Morelos, Mexico, was in the U.S. illegally at the time of his arrest. Advocates argue that he was not informed of his right to diplomatic assistance under an international treaty known as the Vienna Convention on Consular Relations.

Ten years ago, the United Nations' International Court of Justice, also known as the World Court, ordered the United States to reconsider the convictions of 51 Mexicans, including Tamayo, who had been sent to death row without being informed of their consular rights.

Two of the 51 have since been executed, both in Texas.

José E. Medellín, 33, was put to death in 2008 for the 1993 rape and murder of two teenage girls in Houston.

Before his execution, President George W. Bush ordered Texas and other states to review the Mexican nationals’ convictions. But the state's then-solicitor general, Ted Cruz — who is now a Republican senator — persuaded the Supreme Court to rule that the president had no authority to order state courts to honor the World Court’s decision.

At the time, Tamayo and nine other Mexican nationals were on Texas' death row.

Three years later one of them, Humberto Leal, 38, was executed for the 1994 rape and beating of a 16-year-old San Antonio girl.

Mexican officials have tried to stop Tamayo’s execution. Morelos Gov. Graco Ramírez, several Mexican legislators, Mexican Foreign Secretary Jose Antonio Meade, Eduardo Medina Mora, the ambassador to Washington, and National Human Rights Commission President Raul Plascencia have all petitioned the U.S. on Tamayo's behalf.

Last week, former Texas governor and Atty. Gen. Mark White joined the effort.

“As it stands now, Tamayo will become the first person executed without any review of his Vienna Convention claim,” White wrote in the Austin American-Statesman. “I personally support capital punishment. But this case is not about whether we support or oppose the death penalty. It’s about fairness and having the courts hear all the key facts. In Tamayo’s case, a court review could have made a real difference.”

Last fall, Kerry wrote a letter to Perry and Texas Atty. Gen. Greg Abbott urging them to reconsider Tamayo’s execution because it could make it more difficult to help Americans in legal trouble abroad.

“I have no reason to doubt the facts of Mr. Tamayo’s conviction, and as a former prosecutor, I have no sympathy for anyone who would murder a police officer,” Kerry wrote in September. But he added that he was concerned the state’s handling of the case could affect how Americans are treated overseas.