Baghdad, Iraq ? Secretary of State Condoleezza Rice warned Iraqi leaders on Thursday they have limited time to settle their differences and that the escalating waves of violence are intolerable.

On a visit five weeks before congressional elections in the U.S., Rice also insisted the Bush administration has been honest with Americans about the costs and stakes in Iraq.

Administration officials recently have found themselves defending their conduct of the war, and Rice’s remarks reflected the political toll for the White House from an unpopular conflict.

“This is really hard going,” Rice said during her stop in the Iraqi capital. “Not only do I believe that the president has been clear with the American people that this is a struggle, he’s been clear with the American people why he thinks it’s a struggle that needs to be waged.”

After meetings in the Mideast with Arab and Israeli leaders, the top U.S. diplomat came to Iraq to tell sometimes squabbling leaders they have a short window to resolve disputes that she said are spurring sectarian and insurgent violence.

While killings among Iraqis have not abated, American casualties also have spiked recently.

Car bombs killed four people and wounded 28 Thursday in Baghdad. At least 21 U.S. soldiers have died since Saturday; most were in Baghdad amid a massive security sweep by U.S. and Iraqi forces.

In this image released by the U.S. Embassy in Baghdad, Iraqi Prime Minister Nouri al-Maliki and U.S. Secretary of State Condoleezza Rice give a joint statement in Baghdad, Iraq. Rice arrived Thursday in Baghdad for a surprise visit to Iraq.

Rice said the U.S. role is “to support all the parties and indeed to press all the parties to work toward that resolution quickly because obviously the security situation is not one that can be tolerated and it is not one that is being helped by political inaction.”

In a series of meetings with leaders representing most ethnic and religious factions, Rice delivered a blunt message about how Americans do not see the history behind ethnic and sectarian splits, said a senior State Department official present at the sessions.

The official, who spoke on condition of anonymity because the meetings were confidential, said Rice also said Americans need to see Iraqis working together rather than killing one another.