WASHINGTON - A year ago, Vicente Fox enjoyed a unique profile as the foreign leader President Bush had become closest to while governor of Texas. Bush spent a day at the Mexican president's ranch in Guanajuato less than a month after taking office and invited Fox for the first state visit of his young administration.

Fox's abrupt cancellation of his own planned visit to Bush's Texas ranch late this month is a measure of how U.S.-Mexican ties have failed to meet last year's high expectations and of the political price Fox has had to pay at home for staking so much on the relationship.

Fox scrapped his visit to Crawford after Texas went ahead Wednesday with the execution by lethal injection of a Mexican drug smuggler, Javier Suarez Medina, who was convicted of the 1988 murder of an undercover policeman in Dallas.

"This decision is an unequivocal signal of rejection of the execution," Fox spokesman Rodolfo Elizondo said. "It would be inappropriate, in these lamentable circumstances, to go ahead with the visit to Texas."

Fox's snub of what for most leaders would be a prized invitation took the White House by surprise. Only Wednesday afternoon, White House chief of staff Andrew Card told reporters, "I see nothing that suggests the meeting is not going to happen."

Yesterday, White House spokesman Claire Buchan played down the possibility of strains between the two leaders. "President Bush and President Fox share a strong professional relationship, as well as a friendship that represents the deep bonds of our two countries," she said. "And the president very much looks forward to his next meeting with President Fox."

The United States' use of the death penalty has caused strains with many countries, including European allies, but that's only part of the story.

"This is not so much about capital punishment as about sovereignty and about longstanding concerns about the treatment of Mexican nationals in the United States, and particularly along the border," said Bernard W. Aronson, assistant secretary of state for Latin America in the first Bush administration.

Mexico has in the past resisted turning over criminal suspects to the United States. Along with some other countries, it bars extradition in cases where the death penalty might be imposed.

More broadly, analysts say Fox has reason to be disappointed in the returns he has received from his own big political and personal investment in relations with the United States.

During a state visit to the White House last September, he proposed a sweeping change in the immigration relationship between the two countries that over time would allow millions of illegal Mexican immigrants to work in this country legally.

At the time, Bush sounded receptive to a major immigration agreement. But just a few days after Fox's visit, on Sept. 11, terrorists attacked the World Trade Center and the Pentagon, drastically altering Bush's priorities and forcing him to spend time with leaders who were more central to America's war on terrorism.

The administration and Congress became much more cautious about immigration reform, viewing it almost exclusively through the prism of national security. So no agreement has been reached with Mexico.

The U.S. recession has also hurt Mexico through increased economic ties between the two countries after the 1993 North American Free Trade Agreement. This has been particularly embarrassing for Fox, who campaigned for election promising strong economic growth, which has not materialized.

Mexico also became embroiled in a dispute with Texas earlier this year over water. Texas' farmers and politicians were so outraged over what they said was a Mexican violation of a pact on waters from the Rio Grande that Fox postponed a visit to the state set for June.

Fox's pro-U.S. stance has drawn increasing criticism among nationalists in the Mexican Congress, particularly in the opposition Institutional Revolutionary Party (PRI), whose 71-year rule of the country was broken by Fox in 2000. Lawmakers used their power to block a Fox visit to the United States and Canada in April.

"The opposition parties are playing hardball politics with Fox in Mexico and have been for some time," said Meghan Bishop, a Mexico specialist at the Center for Strategic and International Studies here.

With this growing political problem as a backdrop, the execution of Suarez Medina assumed even greater importance for Fox. Mexican officials went to strenuous efforts to prevent it, enlisting support from 12 Latin American governments as well as Spain in appealing to the U.S. Supreme Court for a stay of execution.

Mexico argued that Suarez Medina's rights under the Geneva conventions were violated because he was not put in touch with Mexican consular officials who might have helped with his defense.

Mexico's foreign minister, Jorge Castaneda, telephoned Texas Gov. Rick Perry late last month and Secretary of State Colin L. Powell on Aug. 7. United Nations Commissioner for Human Rights Mary Robinson, whose help Mexico sought, also appealed to Powell.

Fox called the Texas governor and then, Tuesday, reached President Bush "to express his deep concerns at this case" and seek his help in gaining a stay of execution. The White House declined to reveal what Bush said in reply.

The execution "was the straw that broke the camel's back," said M. Delal Baer, also of CSIS, "except that the camel's back is probably not broken."

Fox's action, Baer and other analysts said, serves to inoculate Fox against domestic political damage from the execution. Mexico, she said, was "whistling in the dark" if it expected to change either Bush's or the state of Texas' support for capital punishment.

Strains over executions are likely to recur. Currently, 54 Mexican nationals are on death row across the United States, and Mexican diplomats and lawyers are becoming increasingly active on their behalf.

Mexico has proposed enlisting diplomats from various countries to fight what it calls "the execution of foreign nationals in violation of international law."

But few expect serious long-term damage to U.S.-Mexican relations, which have strengthened substantially in the years since NAFTA was ratified.

"This should not be overplayed. It's a symbolic action," Aronson said.

Sun staff writer Julie Hirschfeld Davis contributed to this article.