Washington ? The CIA has rushed to Iraq four times more clandestine officers than it had originally planned on, but has had little success penetrating the resistance and identifying foreign terrorists involved in the insurgency, according to senior intelligence officials and intelligence experts recently briefed on Iraq.

The CIA mission in Iraq, which was originally slated to have 85 officers, has grown to more than 300 full-time case officers and close to 500 personnel in total, including contractors and people on temporary assignments. It is widely known among agency officials to be the largest station in the world, and the biggest since Saigon during the Vietnam war 30 years ago.

Despite its size, the agency’s efforts to penetrate Iraq’s ethnic factions and to gain intelligence about the insurgency have been hampered by the continued violence, the use of temporary and short-term personnel, and by the pressing demands of military commanders for tactical intelligence they can use in daily confrontations with armed insurgents.

In December, the CIA station chief was replaced with a more experienced officer to handle the unexpected challenges, according to intelligence officials.

The CIA’s role in Iraq is considered crucial to the Bush administration’s hopes for stabilizing the country as it heads toward a June 30 deadline for handing sovereignty to an interim Iraqi government. U.S. military forces are counting on intelligence agents to help identify the leaders and networks behind the flaring insurgency.

With the Bush administration’s war on terrorism spread over five continents, and the hunt for Osama bin Laden intensifying as spring approaches, the agency “is stretched beyond their limits,” even as it makes a historic drive for new recruits, said one senior CIA veteran.