WASHINGTON (AP) _ At a tense moment in U.S.-Mexican relations, a modest request flutters like the flag over the Alamo must have during a battle that raged there 149 years ago today.

Two Lone Star patriots have asked Congress to seek the return from Mexico of the only Texas flag flown over the Alamo still known to exist. The flag is in storage in the Chapultepec Museum in Mexico City. It has been in Mexico since it was cut down during the climactic battle on March 6, 1836.

A rugged band of soldiers held the small San Antonio mission for five days against the huge Mexican army before thousands of Mexican soldiers overran the Alamo. All of the Alamo defenders were killed, including commander William Barret Travis, Jim Bowie and Davey Crockett.

In a letter to ''the people of Texas and all Americans in the world,'' Travis wrote on Feb. 24, 1836, that Mexican President Santa Anna, commanding the army, had demanded surrender.

''I have answered the demand with a cannon shot,'' Travis wrote, ''and our flag still waves proudly from the walls. I shall never surrender or retreat.''

''I don't want this to sound too corny,'' said Corpus Christi oilman Claude D'Unger, ''but there's a certain patriotism when you stop and think 183 people laid their lives on the line, and it's just kind of meaningful to be able to return their flag to them.''

D'Unger, 39, and his neighbor, Navy aviator Clay Umbach, 29, came up with the idea after sitting around one day arguing about the Battle of the Alamo.

''Clay's a hellacious Texas historian,'' D'Unger said. ''I'm more of an agitator.

''We decided to go after the flag and try to have it in the Alamo by the Sesquicentennial (Texas' 150th birthday),'' D'Unger said.

Umbach said they would settle for a loan of the flag for the Sesquicentennial festivities.

The two contacted Rep. Solomon Ortiz, D-Texas, who agreed to carry the banner, so to speak. They are seeking the support of the congressional delegations from 18 states that were represented at the Alamo. So far, 75 members of Congress have indicated support for the action, according to Susan Clark, Ortiz' press secretary.

She said Ortiz asked U.S. Ambassador to Mexico John Gavin to participate and Gavin has contacted Mexico's Museum of Anthropology and Mexican diplomats here. All now await Mexico's answer.

There were likely several flags that flew at the Alamo. The only one known to still exist belonged to the ''New Orleans Greys,'' Louisiana soldiers who fought in Texas' war for independence. Nineteen of the Greys were believed to have died at the Alamo.

Umbach said the flag was cut down during the final battle and taken back to Mexico as proof of American involvement in the Texas war for independence.

In 1950, the United States returned to Mexico 69 flags captured during the war over the annexation of Texas. There was discussion of an exchange for the Alamo flag at the time, but officials decided a trade would make the gestures ring hollow.

In 1965, the Texas Legislature wanted to try again to retrieve the flag, but then-Gov. John Connally said the state had no authority to negotiate with a foreign country.

Umbach said the new flag campaign started before recent tensions between the United States and Mexico over drug law enforcement, but that he and D'Unger are still optimistic the flag will return to the Alamo, now a museum in modern, downtown San Antonio.

Umbach said he and D'Unger are not looking for personal gain.

''I just thought this would be something I'd sure admire were I to walk inside the Alamo and see it hanging on the wall,'' he said.