WASHINGTON – The Senate this week will pull its first all-night debate on the Iraq war in advance of a vote on whether to bring home all combat troops by next spring, Democrats said Monday.

The rare, round-the-clock session Tuesday night through Wednesday morning is intended to bait Republicans into an exhaustive debate on the politically unpopular war, as well as punish GOP members for routinely blocking anti-war legislation.

“How many sleepless nights have our soldiers and their families had?” said Democratic Whip Dick Durbin, D-Ill.

Democrats are trying to ratchet up pressure on Republicans who have grown uneasy with the lack of progress and begun questioning President Bush’s military strategy.

Republicans shrugged off the planned marathon debate as political theater. Minority Leader Mitch McConnell, R-Ky., said GOP senators are “happy to stay and debate this.”

Elsewhere, U.N. Secretary-General Ban Ki-moon warned on Monday that an abrupt U.S. troop pullout could deepen the crisis in Iraq.

Marine Gen. Peter Pace revealed that he and the Joint Chiefs are developing their own assessment of Iraq, to be presented to Bush in September. Options include another troop buildup or maintaining current troop levels beyond September.

Bush on Monday told Iraqi Prime Minister Nouri al-Maliki and other officials that continued U.S. support depends on political progress in Baghdad, said White House spokesman Tony Snow. In a secure video conference lasting more than an hour, Bush “encouraged efforts to build a strong unity coalition and to pass key legislation,” Snow said.

Still, Snow said, “the president reaffirmed his strong support for Prime Minister Maliki.”

Speaking through a translator, al-Maliki told NBC News in an interview: “As soon as we reach this level of readiness, the door will be open for dialogue between us and Americans about our future plans. Now we are thinking as politicians about how to maintain robust long-term relations with the Americans whether they remain on Iraqi soil or pull out from Iraq.”

Former Rep. Lee Hamilton, the Democratic co-chairman of the independent Iraq Study Group, said Monday he’s “extremely doubtful” that al-Maliki will be able to secure the country and allow American forces to leave any time soon.

“There is no chance that the Iraqi forces could take over at any time, or certainly by the first of the year,” Hamilton said in a separate interview on NBC’s “Today Show.”

Associated Press writer Pauline Jelinek contributed to this story