And officials warn the violence may rise as Iraq continues along the road to democracy, with US overseer Paul Bremer due to transfer sovereignty on June 30.

Many people in Baghdad and Karbala, where a series of coordinated blasts on Tuesday killed more than 180 people and injured hundreds of others, blamed the United States for failing to protect them.

"The Americans are the cause of all the trouble and I want them to leave," declared Khalil Ismail, a 35-year-old decorator in the Iraqi capital.

"It is true that there are some terrorists who want to create trouble but they will fail. Iraqi people can secure a stable future on their own," he said.

Following Iraq's deadliest day of violence since the fall of Saddam, senior Shia Muslim clerics, whose followers make up more than 60 percent of the population, also pointed the finger at the United States.

"We hold the occupying forces responsible for being unwilling to control the borders of Iraq and stop intruders," said a statement from the office of the country's leading Shiite cleric, Ayatollah Ali Sistani.

The coalition, however, defended itself arguing that it was impossible to prevent 100 percent of the attacks 100 percent of the time.

"Terrorists have to be successful once in a while to be very successful," said Coalition Provisional Authority spokesman Dan Senor.

"To protect against terrorism we have to be successful every single time," he told a news conference on Tuesday, adding that this was an impossible feat.

For his part, US Brigadier General Mark Kimmitt said that his troops' ability to fight the insurgency, which appears intent on sparking a civil war between the Shia and Sunni Muslim communities, was improving.

"We have a high level of security across the country all the time," Kimmit told reporters on Tuesday.

"We hope to get better every day. We hope that every time there is an attack like this, it is one last trick the terrorists can use."

Such assurances, however, do little to quell the resentment on the street.

"We are occupied by the Americans but they are not helping us," said Moki Abu Daga, an ice cream and candy shop owner in the holy city of Karbala south of Baghdad.

He shut his shop minutes before explosions destroyed the dreams of hundreds of thousands of Shias the previous day who had gathered in the city to mark the climax of the solemn 10-day Ashura festival for the first time in decades.