The $50 billion question this week is: When will the White House ask Congress to pony up more money for the United States’ occupation of Iraq?

Despite all the media attention focused on the Bush administration’s planning — or, some might say, lack thereof — for post-war Iraq, a new supplemental funding request could become the

tripwire that sets off a rematch between the White House and Congressional penny-pinchers over whether the U.S. should require a future Iraqi regime to pay back reconstruction funds.

It seems like eons ago, but it was only last October that the Senate narrowly voted to require Iraqis to pay back $10 billion of the $87 billion destined for Iraq in a supplemental appropriations bill. Then the White House put the kibosh on House appropriators’ efforts to do the same, and in the end the proposal was omitted from the final conference report.

Now, a quick survey of lawmakers who got rolled by the White House in last year’s debate suggests the Bush administration probably has good reason for procrastinating.

“I’ve been thinking about what’s been transpiring in Iraq and thinking it would have been a good idea to require loans from the Iraqi people, so that they feel they have more of a stake in their future,” said Sen. Olympia Snowe (R-Maine). Snowe suggested that the recent uprisings in Iraq might have been muted if the Iraqis knew they had to repay the United States for the damage.

Sen. Ben Nelson (D-Neb.) added that it will be essential for the United States’ fiscal health to require the Iraqi people to take on some of the costs of their own reconstruction.

“I would intend to raise the question again” about the loan proposal, Nelson said. “We obviously had enough votes in the Senate last year. … $5.2 trillion of [Iraqi] oil reserves is an awful lot of collateral to support at least partial repayment.”

Such banter is starting to grow achingly familiar. With Members beginning to assume that another astronomically priced supplemental is on its way, they are gearing up for an encore presentation of payment plans for the Iraqi people.

The White House, for one, seems to be inching away from President Bush’s repeated vow that he wouldn’t ask for more money this year — well, at least not until November, once Republicans have safely won the presidential and Congressional elections. Bush recently toned down his proclamations about the sufficiency of current funding levels for Iraq, and he promised that if military commanders request more money earlier than planned, he will ask Congress for it.

Hearing that, Members now speculate that the White House could come begging Congress for $50 billion or more — as early as this summer.

The Bush administration is already having a hard time convincing some members of its own party to scrap their spending-restraint rhetoric to make way for deeper tax cuts this year. This intraparty fight has been laid bare in the continuing House-Senate stalemate over the budget resolution.

Plus, the White House has been taking a good deal of heat from both Republicans and Democrats over the fact that they included a grand total of $0 for war efforts in Iraq and Afghanistan in their 2005 budget request.

So it should come as no surprise that Congress is demanding to know exactly when the administration will be asking for another supplemental spending bill — and how much they’ll be adding to the federal deficit in the process.

That’s why fiscal conservatives in both parties, along with some Democrats seeing a political winner in attacking the White House’s Iraq policy, have already begun sharpening their knives.

“The administration has misled us on the reason for this war, the duration of this war, and the cost of this war,” said Sen. Dick Durbin (D-Ill.), who noted that “of course” the Iraqi loan issue and other ways of offsetting the costs of the war would come up in any potential supplemental debate this year.

But one senior Senate GOP aide cautioned Members to keep their daggers sheathed — for now.

“I’ve heard rumblings [about a supplemental], but I’ve never heard anything credible from anybody whose hands are actually on the wheels,” said the aide. “All indications have been that there won’t be a supplemental request.”

Just in case, Sen. Joseph Biden (D-Del.) said he would likely reoffer his amendment to scale back President Bush’s previously passed tax cuts in order to pay for the war.

And Sen. Byron Dorgan (D-N.D.) said he would again pursue his plan to use Iraqi oil revenues to make up for some of the costs of the U.S. occupation and reconstruction.

Dorgan added that he also might try to dip into the $20 billion Congress designated last year for Iraqi reconstruction. Much of that money has not yet been spent because the escalating violence in Iraq has hampered the ability of contractors to complete work on vital infrastructure needs, said Dorgan.

The unwillingness of Congress to leave U.S. troops without needed equipment means “they’re going to get the funding,” Dorgan said. “But I do think we ought to have a discussion with the administration about how do you plan to pay for this. And that discussion ought to come sooner rather than later.”

Indeed, many Members — especially appropriators — have been pressing the administration to come forward with a supplemental funding request relatively soon, so that it might be able to move in tandem with the regularly scheduled $400 billion-plus Defense Department appropriations bill.

If recent history is any guide, the Senate may again be the staunchest advocate for making sure U.S. taxpayers aren’t left holding the bag. But don’t count out House conservatives just yet.

Rep. Mark Kirk (R-Ill.) — a loan supporter last year — implied that the Bush administration didn’t heed Congress’ request for disclosure on the full cost of the war and reconstruction when the White House failed to include funding for Iraq and Afghanistan in its February budget request.

“It’s not realistic to put forward a budget that did not acknowledge that we have troops in Iraq,” said Kirk.

Kirk said he wouldn’t necessarily revive the loan proposal on the House side, because he was generally satisfied that the House and Senate Budget Committees filled in the administration’s Iraq funding gap in their respective budgets.

The House-passed budget assumes a $50 billion hit to the deficit, based on estimated Iraq costs this year. The Senate budget included a $30 billion reserve fund for the war. The two chambers are expected to come to a budget deal later this week or next.

But Kirk warned, ominously, that if the White House makes a supplemental request this year for more than $50 billion, “we’re going to have to look for cuts elsewhere to make up the difference.”