Baghdad, Iraq ? An American soldier was killed in a roadside bombing north of Baghdad, the U.S. military said Friday, making April the deadliest month for American forces in Iraq this year.

Al-Qaida’s No. 2 leader issued a video saying that hundreds of suicide bombings in Iraq have “broken the back” of the U.S. military – the latest in a volley of messages by the terror network’s most prominent figures.

Ayman al-Zawahri, an Egyptian militant believed to be hiding in Afghanistan or Pakistan, said that U.S. and British forces had bogged down in Iraq and “have achieved nothing but loss, disaster and misfortune.”

American troops, acting on tips from Iraqi intelligence, meanwhile, killed the reputed al-Qaida boss of Samarra, where a Shiite shrine bombing two months ago nearly plunged the country into civil war.

The latest American death, which occurred Thursday evening, brought the number of U.S. troops who have died this month in Iraq to at least 69.

Although that figure is well below some of the bloodiest months of the Iraq conflict, it marks a sharp increase over March, when 31 American service members were killed. January’s death toll stood at 62 and February’s at 55. In December, 68 Americans died.

The increase in U.S. deaths comes at a time when the U.S. military says sectarian violence among Iraqis is declining after a sharp rise in the wake of the Feb. 22 bombing in Samarra. That triggered reprisal attacks against Sunni mosques and clerics.

In a briefing Thursday, Maj. Gen. Rick Lynch told reporters that sectarian attacks in the Baghdad area had fallen by 60 percent last week, diminishing fears of civil war.

A U.S. Marine pays respects to Lance Cpl. Stephen J. Perez, of San Antonio, Texas, who was killed in a mortar attack on April 13, 2006, at Camp Fallujah, 65 kilometers (40 miles) west of Baghdad, Iraq, Friday, April 28, 2006. At least 2,397 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Al-Qaida in Iraq leader Abu Musab al-Zarqawi warned in an Internet video earlier this week that U.S. “dreams” in Iraq “will be defeated” and “what is coming is even worse.”

The 16-minute video by al-Zawahri, posted today on an Islamic militant Web forum, also came within the same week as an audiotape by al-Qaida’s top leader Osama bin Laden.

Al-Zawahri said that al-Qaida in Iraq “alone has carried out 800 martyrdom operations (suicide attacks) in three years, besides the sacrifices of the other mujahedeen, and this is what has broken the back of American in Iraq.”

The video was first obtained by IntelCenter, a U.S. contractor that provides counterterrorism intelligence services to the U.S. government. A U.S. counterterrorism official, speaking on condition of anonymity in compliance with office policy, said it was part of al-Qaida’s ongoing propaganda blitz to demonstrate the terror group remained relevant.