Updated

Senate Democrats, including several prospective presidential candidates, charged Thursday that the Bush administration's optimistic assessments on Iraq are not borne out by events on the ground.

Testifying for the administration at a Senate Foreign Relations Committee hearing, the U.S. ambassador to Iraq, Zalmay Khalizad, said the political progress that has been made in Iraq "has created opportunities and put Iraq on the right trajectory."

But Sen. Joseph Biden of Delaware complained there was a lack of a coordinated plan to combat violence in Iraq and said Sunni Arab participation in the political process remains marginal.

"If we do not meet these challenges, we risk trading a maniacal dictator for chaos," said Biden, the committee's ranking Democrat.

Sen. John Kerry, the defeated Democratic nominee for president in 2004, cited figures to show that violence in Iraq is up sharply since Saddam Hussein was forced from power in April 2003.

Kerry, D-Mass., said the violence is such that some Iraqis are saying the country is in a state of civil war.

Wisconsin's Sen. Russ Feingold, another prospective Democratic presidential candidate, said there is "no real clarity" as yet on when American forces in Iraq will come home.

Khalilzad acknowledged that serious problems exist but said that "a path exists to success in Iraq."

"The struggle for the future of Iraq is vital to the future of the world," he said. "If Iraqis work together against terrorism and sectarianism, and if Americans and other friends of Iraq support them, we will succeed."