Formerly headed by Dick Cheney, the US vice president, the company won contracts in Iraq following the US-led invasion in 2003, some of which were awarded without going to tender.

Opportunistic

"This is an insult to the US soldiers and taxpayers who paid the tab for their no-bid contracts and endured their overcharges for all these years," said Patrick Leahy, Democratic senator and chairman of the judiciary commitee.

Henry Waxman, a representative and chairman of the Oversight and Government reform committee may hold a hearing on the implications, according to an aide.

"They are being opportunistic in putting the CEO in the middle of the action," said William Sanchez, an analyst at Howard Weil.

He said he believed the move was not tax-related, but strategic, a view backed by another analyst, Alan Laws of Merrill Lynch, who said the move would help Halliburton's position in negotiating large contracts.

Halliburton is also in the process of splitting off its engineering and military services contracts unit, KBR, which is the Pantagon's largest contractor in Iraq.

KBR already has more than $20 billion in revenues from its Iraq contracts and has been the target of several investigations into its billing practices and complaints from some US politicians about its close ties to the Bush administration.