By Steven Lee Meyers and Thom Shanker
The attacks - 23 in the past month, including 2 on Wednesday - have alarmed American officials and raised questions about the ability of Iraq's security forces to stamp out attacks on the capital's governmental and diplomatic core.
They have coincided with President Obama's declaration of the end of the American combat mission here on Aug. 31 and the fitful, convoluted negotiations among Iraq's major political blocs to choose a new prime minister and thus a new government.
The attacks have not been particularly accurate or lethal, although in the past week at least two people were killed in Karada, a neighborhood in a sharp bend of the Tigris River opposite the Green Zone, or international zone, where Iraqi government offices and foreign embassies are concentrated.
But the intensity of the attacks has compounded a sense of anxiety here - and back in Washington - as Iraq's political impasse drags on almost seven months after parliamentary elections in March.
One rocket last week crashed into the home of the former speaker of Parliament, Mahmoud al-Mashhadani, wounding several people. At the American Embassy, "duck and cover" sirens have become a regular occurrence.
"It's very difficult to do diplomacy and development without adequate security," Secretary of State Hillary Rodham Clinton said at a conference on Tuesday in Washington, though she did not directly address the recent attacks.
"So as our troops go out of Iraq, which is the plan, then we have to figure out how do we provide enough of a security envelope for our diplomats and our development experts to do the work that we're now asking them to do."
The recent attacks have been so worrisome that the Pentagon's civilian and military leaders were briefed on them last week. At least two of the rockets struck the sprawling American Embassy compound in late August, but there has not been a fatal attack there since July, when a rocket killed three foreign security contractors and wounded 15 people, including two American citizens.
Defense Secretary Robert M. Gates, during a meeting on Wednesday with R.O.T.C. students at Duke University, argued that a substantial American commitment to Iraq would be required to sustain progress there. In particular, he criticized Congress for cutting the State Department's request for money he said was required for the American Embassy to take the lead in Baghdad with the end of the American combat role.
Unlike the recurring carnage carried out and claimed by Al Qaeda in Mesopotamia and other Sunni insurgent groups, the rocket attacks are a signature of Shiite extremist groups, some of them affiliated, at least loosely, with political parties now vying for political power.
They include the Promised Day Brigade, allied with the anti-American cleric Moktada al-Sadr, whose followers won 39 seats in the new 325-member Parliament and have since emerged as a potent bloc in the political negotiations.
The Sadrists have joined a still shaky alliance with other Shiite parties and Prime Minister Nuri Kamal al-Maliki's bloc, but they oppose Mr. Maliki's election to a second term in office. A self-imposed deadline to select a unified candidate within the alliance passed on Monday night, with leaders saying they needed more time.
"There is a political component behind indirect fire attacks," the American military commander in Baghdad, Brig. Gen. Ralph O. Baker, said Wednesday, using the military argot for rocket or mortar attacks. "Maliki has run on a platform of improved security, and it's conceivable that if rockets land in the international zone, then it discredits his security platform and makes him vulnerable from a political standpoint as these negotiations are occurring."
General Baker and other commanders here blamed Iran for training and equipping the Shiite militias. In an interview on Tuesday, the chief American military spokesman, Brig. Gen. Jeffrey S. Buchanan, attributed the attacks to "at least some elements in Iran," if not the government directly. "They're capable of turning up the heat and turning it down," he said.
Attacks like the recent ones have long harassed those inside the Green Zone or in the neighborhoods on the flight path. The frequency has risen and fallen, often without clear pattern, though the Green Zone seems to be a target when Vice President Joseph R. Biden Jr. visits.
Most of the rockets are fired from predominantly Shiite neighborhoods on the eastern side of Baghdad, though one fired on Wednesday came from Kadhimiya, the neighborhood west of the Tigris that includes one of the holiest shrines for Shiites in the capital.
So far this year, there have been 134 rocket or mortar attacks in Baghdad, according to figures provided by General Baker's command. Each attack can include one or more rockets. Of those, 49 have come in the past 90 days. Rocket and mortar attacks have also struck American bases around the country, killing an American soldier, Sgt. Brandon E. Maggart, in Basra on Aug. 22.
Sophisticated American radar systems can trace attacks to their source even before the rockets land, but with American troops having withdrawn from cities, the task of catching those firing them has fallen to Iraqi security forces, with mixed results.
The insurgents have also adapted, often placing the rocket systems in remote areas with timers set to launch the rockets after they depart. "It could be as simple as a washing machine timer," General Baker said.
He said that the protracted political impasse had resulted in waning confidence among Iraqis, who, he added, had shown a greater willingness earlier in the year to pass information about insurgents to the authorities. That resulted in tips that led to a series of arrests of extremists associated with Al Qaeda in Mesopotamia and other groups in the spring.
"I would argue that the level of confidence is not to the degree where they're supporting insurgent groups anymore," the general said of Iraqis, "but that they're essentially fence-sitting. They're sitting on the fence trying to see which way this is going to play out. When they do that, the tendency to share the kind of information the security forces need to be highly effective diminishes somewhat."
