BAGHDAD, Iraq – The U.S. military nearly set off a sectarian crisis yesterday by mistakenly arresting the leader of Iraq’s top Sunni Muslim political party, while two suicide bombers killed about 30 police, and American fighter jets destroyed insurgent strongholds near Syria’s border.

Northeast of Baghdad, an Iraqi military aircraft crashed yesterday during a mission with four American troops and one Iraqi on board, the U.S. military said. It was not immediately clear what their condition was or even what kind of aircraft it was.

A spokeswoman for the American military in Baghdad, Sergeant Kate Neuman, said the four Americans were military personnel.

And on Memorial Day, the military said an American soldier, Specialist Phillip Sayles of the 1st Battalion, 24th Infantry Regiment, was killed in an attack Saturday in the northern city of Mosul. As of yesterday, at least 1,657 members of the American military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

The arrest of Iraqi Islamic Party leader Mohsen Abdul-Hamid, his three sons, and four guards did little to help efforts to entice Iraq’s once-dominant Sunni community back into the political fold. The Sunnis lost their influence following Saddam Hussein’s ouster two years ago.

Many believe the Sunni fall from grace, and parallel rise to power of Iraq’s majority Shiite population, is spurring the raging insurgency, driving many disenchanted Sunnis to launch attacks that have killed more than 760 people since the April 28 announcement of the Shiite-dominated new government. Bringing Sunnis back into the political fold could soothe some tensions.