By Alastair Macdonald

TIKRIT, Iraq (Reuters) - An audio tape purportedly from former Iraqi
President Saddam Hussein broadcast on Tuesday vowed to defeat the United States to avenge the deaths of his two sons by U.S. forces.

"I mourn to you the deaths of Uday and Qusay and those who struggled with them... America will be defeated," said the voice on the tape, aired by Dubai-based al Arabiya television.

"They...died martyrs in the name of jihad (holy war)," the voice said.

The speech was rambling, breaking off in mid-sentence on occasions, but a Reuters correspondent familiar with Saddam's voice said it sounded like the deposed dictator. The CIA said it was trying to determine whether the tape was genuine.

A number of tapes purportedly from Saddam have been broadcast in the past few weeks, but this was the first to refer to the killing of his two sons by U.S. troops last Tuesday in a bloody raid on a villa in the northern Iraqi city of Mosul.

The U.S. military said troops hunting Saddam had captured three key figures loyal to the former Iraqi leader, including a top bodyguard, and were closing in on Saddam himself.

Major Josslyn Aberle told Reuters one of the captured Saddam loyalists put up a brief struggle and that two gunshots were heard as the raid began in the area of Saddam's home town of Tikrit, north of Baghdad. There were no U.S. casualties.

Television pictures filmed through a night vision lens showed a man being escorted from a building by U.S. soldiers, blood seeping through a blindfold.

U.S. troops believe Saddam may be hiding somewhere in the Tigris valley of dusty tomato fields and orchards.

U.S. Deputy Secretary of State Richard Armitage said U.S. forces nearly captured Saddam in raids on Monday near Tikrit.

"I think most people feel...the noose is tightening pretty regularly around
the neck of Saddam Hussein," he told CNN.