No matter how elusive or shadowy are the terrorists who bombed two American embassies in Africa, U.S. officials vow they will be tracked down. Experience has shown that can be a long and frustrating process, which has had mixed results.

President Clinton led the voices of determination. The bombers will be brought to justice, he said in his Saturday radio address, "no matter how long it takes or where it takes us."It's a pursuit that can consume years, officials acknowledged Friday, only hours after the attacks on the U.S. missions in Kenya and Tanzania. But they insisted Washington has a long memory in these cases.

"We don't forgive. We don't forget," observed P.J. Crowley, spokes-man for the National Security Council.

Even so, it has been a full two years since a major attack against a large U.S. facility in Saudi Arabia, and no one has been held accountable. The bombing of the Khobar Towers housing complex on June 25, 1996, killed 19 U.S. airmen and wounded 500.

The attack forced movement of thousands of American military men and women for their own protection into near prison-like encampments inside Saudi Arabia. It also instigated tightened security at American military installations around the globe.

Like the shadowy Khobar Towers bombers, those who set off the explosions in Africa that claimed more than 100 lives - among them at least 11 Americans - have given little hint so far of who they are or the message they were trying to send. That can make it even harder to find them, U.S. officials say.

Defense Department intelligence officials and other government analysts said no warning came to the embassy in either capital, Nairobi, Kenya, or Dar es Salaam, Tanzania. The officials spoke on condition of anonymity.

In recent months overseas installations have reported more instances of individuals who ap-peared to be looking them over in suspicious ways, a government official said. But the official said no overt threats were received that could have foreshadowed the African bombings.

He said the two attacks required many months of planning, obvious because of the size of the bombs, the attacks' coordinated timing and the relatively easy targets that were chosen. Neither embassy had been updated with recent anti-terrorist blast protections.

U.S. intelligence officials will pore over records and other reports for any hint of what might have been intended as a warning, a defense official said. The official said finding such a signal, even after the fact, could help find the perpetrators.

Despite the lack of progress made on the Khobar Towers bombing, the security council's Crowley reminded reporters: "We've had some success - some cases you've heard about, some cases you haven't."