WASHINGTON, May 7 (Reuters) - Timothy McVeigh, scheduled tobe executed for the Oklahoma City bombing that killed 168 people, will die a loner whose violent act never resounded with extremist groups nor generated a sympathetic band of followers, U.S. terrorism experts say.

In the six years since McVeigh exploded a truck bomb outside the Alfred P. Murrah federal building in retaliation for a government raid on a religious compound in Waco, Texas, federal authorities have kept a closer eye on militia and extremist groups. But the feared ripple-effect from McVeigh's act never materialized.

McVeigh appears to have been an anomaly in committing the worst act of domestic terror in U.S. history, experts say.

"McVeigh thought with his act that that was going to be an opening salvo in a white supremacist revolution that would sweep over the country," said Bruce Hoffman, a terrorism expert at RAND.

"McVeigh really thought that he would strike a responsive chord throughout the U.S.," he said. "Six years later that revolution has never materialized."

At the time of the 1995 Oklahoma City bombing, anti-government militia groups around the United States were flourishing in part due to deadly confrontations between federal agents and fringe groups advocating a range of ideas from white separatism to gun rights.

In 1992, a furor erupted over a deadly shootout involving U.S. agents at the Ruby Ridge, Idaho, home of Randy Weaver. In 1993, the 51-day standoff between the Branch Davidians and federal law enforcement agents in Waco rallied government critics, who denounced it as a symbol of excessive force.

But even groups with fierce anti-government doctrines shunned any public association with McVeigh's act.

One reason is, the Oklahoma City bombing was perceived as an assault on innocent lives, particularly the 19 children who died, rather than on a symbol of the government, experts say.

NO HERO

McVeigh bombed the Murrah building on April 19, 1995, the second anniversary of the fiery end to the siege at Waco in which about 80 Branch Davidians died when their compound burned down after federal agents tried to force them out using tanks and tear gas.

Waco generated national debate about the role of government versus the rights of groups outside mainstream America, while Oklahoma City led the government to intensify security around federal buildings.

"I don't think McVeigh has become a hero within the militia movement at all," Da???iate policy analyst at the Cato Institute, said from Colorado.

"Even if you take his point of view and accept it all down the line, blowing up a bunch of kids is so far out of line of what even the most extreme person might think is acceptable," Kopel said.

"It was recognized as an act of???ted aggression against innocent people, I don't think there's a lot of feeling that killing a bunch of people who process Social Security checks is some kind of legitimate response."

McVeigh, scheduled to die by lethal injection on May 16 at a prison in Terre Haute, Indiana, was not expected to attain martyr status that would lead to violent acts by others to remember him on the anniversary of his death, experts said.

"McVeigh is someone who will be forgotten. It's not a broader movement," said John Parachini, executive director at the Monterey Institute think tank.

FBI STATISTICS

RAND's Hoffman said: "A complete failure in life, basically an abject child killer rotting away in prison, he's hoping to transform himself in death at least into precisely the type of martyr that he feels may accomplish what he couldn't do when he was living."

The most recent FBI statistics from 1998, show incidents of domestic terrorism declined in the 1990s from the previous decade. But fatalities were higher in the 1990s.

The FBI report said 39 domestic terrorist incidents occurred on U.S. soil between 1990 and 1998, including pipe bombs, arson, and abortion clinic bombings.

That compared with 220 incidents in the 1980s in which 26 people were killed, while 176 were killed in the 1990s -- mainly due to Oklahoma City, Hoffman said.

That showed Oklahoma City was "the aberration, not the pattern," he said. "What you could really conclude is the vast majority of terrorist incidents in the United States are non-lethal," Hoffman said.

The FBI is careful to say it investigates individuals suspected of crimes, and not groups because of their leanings.

"We don't track militia groups. Militia groups have a right to assemble. We go after individuals who commit crimes," an FBI spokesman said. "Domestic terrorism continues to be a concern of the FBI in all of its forms."

The U.S. Senate plans to hold hearings on terrorism this week to focus on how the United States can better prepare for the potential of violent acts on U.S. soil.

McVeigh "was a home-grown terrorist. This was not a terrorist that we expected," said Senate Intelligence Committee Chairman Richard Shelby.

But lessons learned from the Oklahoma City bombing helped foil "the millennium scare" at the end of 1999 when there were threats against Americans, the Alabama Republican said.