U.S. officials have called Emad Husayn Abdullah al-Ani the father of Iraq's program to make the sophisticated nerve agent VX. His capture could be an important advance in the U.S. search for chemical and biological weapons inside Iraq. 

U.S. officials also have accused al-Ani of involvement with an alleged chemical weapons plant in Sudan with links to al-Qaida. 

Military officials say U.S. troops have found no confirmed chemical or biological weapons so far in their searches inside Iraq. No evidence of links between Iraq's government and the al-Qaida terrorist group has been found, either, military officials say. 

If he cooperates with the Americans, al-Ani may be able to provide information on both. He is not one of the "most wanted" Iraqis depicted on the deck of cards distributed by the Pentagon. 

Al-Ani was involved in Iraq's development of the nerve agent VX, one of the world's deadliest chemical weapons - and a substance that is difficult to make. He once headed the research and development program at Iraq's Muthanna State Establishment, a key chemical weapons laboratory, and later headed Iraq's Fallujah 2 chemical weapons plant. 

In 1998, U.S. officials said al-Ani had links with executives of the Shifa Pharmaceuticals plant in Khartoum, Sudan. Then-President Clinton alleged that the plant was making a key precursor chemical used in manufacturing VX, a claim that was never independently substantiated. 

American officials said the Shifa executives who had contact with al-Ani also had ties to al-Qaida leader Osama bin Laden. But they conceded they did not know if al-Ani or other Iraqis knew of Shifa's links to bin Laden, which the U.S. officials said were "fuzzy." 

The United States destroyed the plant with cruise missiles shortly after al-Qaida bombed U.S. embassies in Kenya and Tanzania. Officials of the Shifa plant and Sudan's government denied it was involved in chemical weapons work. 

At the time, Iraq's government denied al-Ani was working with Sudanese authorities and said he had never visited Sudan. That statement, however, said Iraq never produced stable VX precursors, when United Nations weapons inspectors concluded Iraq had made tons of VX. 

U.S. officials said they had electronically intercepted telephone calls between al-Ani and Shifa plant executives.