Aug. 9 (Bloomberg) -- Iraq's western Anbar province remains the most deadly place for U.S. forces in the country, with at least 21 Marines killed in hostilities there since the handover of authority to an interim Iraqi government, according to U.S. military figures.

The toll of combat deaths in Anbar, west of Baghdad, has mounted even as Marines battle loyalists of renegade cleric Moqtada al-Sadr in southern Iraq, and accounts for a third of Americans tallied as killed in action since the June 28 transfer of political power. At least four Marines were killed in the past week there, including one yesterday, in what military statements posted on the Pentagon's Web site describe only as ``enemy action.''

Anbar, the central part of the so-called ``Sunni Triangle,'' contains the cities of Ramadi and Fallujah, bastions of resistance to the U.S.-led stability and rebuilding effort. U.S. Marines turned over control of Fallujah to an Iraqi unit after mounting a siege that killed scores of suspected fighters.

A Marine Corps spokesman said convoys are routinely attacked using homemade bombs placed along known travel routes.

``The place is just littered with explosives, ammunition and weapons,'' First Lieutenant Nathan Braden at Camp Pendleton, California, said in a telephone interview. The insurgents are ``very creative,'' Braden added. He declined to discuss techniques used by anti-U.S. fighters.

``It's definitely not pitched battle,'' Braden said.

Anbar, Iraq's largest province, touches the desert borders of Jordan, Syria and Saudi Arabia, allowing fighters to enter Iraq across a remote area spanning hundreds of miles.

Border Promises

George Sada, the spokesman for Iraq's interim Prime Minister Ayad Allawi, said Allawi visited Syria, Jordan and Saudi Arabia and has won commitments to increase cooperation on border control.

``They promised the prime minister they would fix the borders and not let people in,'' Sada said from Baghdad in a telephone interview. Sada said Allawi's government also hopes a limited amnesty will prompt fighters to lay down their arms.

The insurgency means Allawi's government will continue to look to the U.S. to maintain its presence in Anbar, Sada said.

The 1,000 Marines in Ramadi began in late June to focus on securing the main highway from central Ramadi to three nearby U.S. camps, the Christian Science Monitor newspaper reported last month from the area. In addition to combat deaths, the Marine battalion has had at least 180 of its personnel wounded since March, mostly due to ambushes and roadside bombs, according to the Monitor.

Colonel Killed

Among the dead was Lieutenant Colonel David Greene, 39, a reservist assigned to an attack-helicopter squadron, a Pentagon statement said. Greene piloted an AH-1 Cobra helicopter and was hit July 28 by ground fire while flying in the province, the Associated Press reported.

U.S. military officials have said they suspect alleged al- Qaeda associate Abu Musab al-Zarqawi and his followers may be using Fallujah as a base. U.S. aircraft have repeatedly attacked suspected safe houses for Zarqawi's network in Fallujah, a Sunni Muslim city of about 250,000 people.

In central and southern Iraq, U.S. soldiers are trying to quell an uprising instigated by al-Sadr in the holy city of Najaf and in the Baghdad slum of Sadr City. The renewed violence in Najaf since Thursday has killed more than 360 fighters of al- Sadr's militia, according to the U.S.

``The main challenge is quite obvious: it's security,'' Richard Armitage, the U.S. deputy secretary of State, said in an interview Thursday with the London-based al-Hayat newspaper. ``And moreover, it's generally the security situation in what we call the Baathist Triangle.'' The reference is to the Baath Party of former dictator Saddam Hussein.

Outside Anbar, insurgents have mounted fatal attacks against U.S. soldiers in Baghdad, where at least a dozen have died since June 28, Samarra and other areas of resistance.

Iraqis Attacked

Iraqis have suffered the worst casualties since the handover. Among the most deadly post-June 28 attacks was the July 28 car bombing in front of a police station in Baqubah, killing about 70 people and wounding 65. Churches in Baghdad were attacked on Aug. 2, killing at least 11 Iraqis.

Anbar ``is a great big empty desert, and it's filled with Bedouin tribes,'' Patrick Lang, a former chief Middle East analyst at the Defense Intelligence Agency, said in an interview. ``They identified with the previous government.''

``They tend to be warlike, and are into banditry,'' Lang added. ``They don't like foreign intervention in the area, so they side with the insurgency.''

To contact the reporter on this story: Todd Zeranski in New York at tzeranski@bloomberg.net

Last Updated: August 9, 2004 13:57 EDT