BAGHDAD, Iraq (AP) – Iraqi forces for the first time took over security responsibility for an entire province Thursday, a milestone in the American plan to transfer control of the entire country by the end of next year.

British Maj. Gen. John Cooper signed the document turning over responsibility for Muthanna province, a relatively peaceful, sparsely populated Shiite province that had been under British and Australian control.

“It is a great national day that will be registered in the history of Iraq,” Prime Minister Nouri al-Maliki said in a ceremony in the provincial capital of Samawah. “This step will bring happiness to all Iraqis.”

The strategy of transferring all 18 provinces to Iraqi control depends on the capability of Iraq’s newly trained police and army to maintain order against threats by Sunni insurgents and sectarian militias. During the handover ceremony, al-Maliki warned that “the terrorists” were bent on upsetting the process and destroying Iraq’s national unity.

“They will spare no effort to destroy this step and ensure that no further steps are taken,” al-Maliki said. “But, with solidarity and patience, you will cut off the hands that want to sabotage this region.”

Iraqi forces marched in formation past the prime minister and other dignitaries at a stadium in Samawah, a city about 230 miles southeast of Baghdad. Local tribal leaders wearing traditional Arab headdresses and robes then approached the dignitaries’ tent, waving rifles and chanting, “We are ready to die defending this soil.”

“We were and are helping to build a strong peaceful democratic society in Iraq,” Cooper said. “Today is an important step in that process.”

Only about 700 British and Australian troops were stationed in Muthanna, along with about 600 Japanese soldiers on a separate humanitarian mission. The Japanese troops are in the process of leaving the country, while the British and Australians will redeploy elsewhere in southern Iraq to stand in reserve in case the Iraqis need help with security.

Nevertheless, the handover marked a major step in the transformation of Iraq since the 2003 U.S.-led invasion and the collapse of Saddam Hussein’s regime.

Coalition forces are expected to hand over responsibility soon in other quiet southern provinces.

If all goes well, the U.S.-led coalition plans to transfer responsibility for the 17 other provinces by the end of next year.

U.S. and other international troops would then step back, allowing the Iraqis to run security while staying in reserve in case of a crisis. That would be followed by a third stage in which U.S. troops would leave Iraq.

National security adviser Mouwafak al-Rubaie said he was confident the Iraqis could meet the challenge in Muthanna, where he acknowledged the threat of violence was low.

“But with this particular province, I believe this is a huge step forward in Iraqis taking control of the fate of their country,” al-Rubaie told CNN’s “American Morning.”

Gen. George Casey, the top American commander in Iraq, and U.S. Ambassador Zalmay Khalilzad welcomed the handover.

“The handover represents a milestone in the successful development of Iraq’s capability to govern and protect itself as a sovereign and democratic nation,” they said in a statement.

British Defense Secretary Des Browne said the move puts the Iraqis “one step nearer to assuming full responsibility for their own security and to building a stable and democratic future for their country.”

Nevertheless, violence continued Thursday, although at a lower level than in recent days. At least 31 people were killed, mostly in Baghdad and surrounding provinces, police said,

A U.S. Army attack helicopter crashed Thursday during a combat patrol southwest of Baghdad but the two pilots survived and returned to duty, the U.S. command said. The statement did not say why the AH-64D Apache Longbow crashed or give a specific location.

Iraqi authorities said the helicopter was shot down near Youssifiyah, 12 miles southwest of Baghdad in an area where al-Qaida in Iraq and other insurgents operate. The Iraqis spoke on condition of anonymity because they are not authorized to talk to media.

The U.S. military announced that an American sailor was killed Wednesday in Anbar province west of the capital.

U.S. military deaths have dropped sharply this month, with 11 American fatalities reported so far in July. The military said 62 Americans died in June and 69 in May.

But the decline in U.S. losses has been coupled with a sharp rise in sectarian violence in Baghdad and surrounding provinces targeting civilians from the Shiite and Sunni communities.

The ministers of defense and interior appeared before parliament Thursday to discuss the security crisis in Baghdad. Most of the session was closed for security reasons.

During the public part, Defense Minister Abdul-Qader al-Mifarji, a Sunni, acknowledged that security in the capital was worsening. He said Iraqi forces were trying their best to curb the unrest but “those extremists kill in a very swift way so that we cannot react quickly.”

AP-ES-07-13-06 1831EDT