HELENA -- Lawmakers acknowledged they may not be able to finish their work by Friday's scheduled end of the 2007 Legislature following collapsed budget negotiations, saying a lengthy special session may be needed.

The body appears unable to reach a compromise on budget and tax cut plans, legislative leaders said.

It would be the first time in recent memory that the Legislature failed to adopt a state spending plan -- the body's primary responsibility -- during its regular 90-day session, according to observers and legislative staff.

But the possibility loomed large Wednesday with just two days left.

''I don't know what's going to happen,'' said Senate President Mike Cooney, D-Helena. ''It's a very volatile situation.

''Nobody has ever seen anything quite like this.''

Negotiations, which were hardly going anywhere anyway, completely fell apart Wednesday morning when House Majority Leader Michael Lange, R-Billings, announced an impasse amid a profanity-laced attack at the governor. Key conference committees charged with finding solutions on important bills were promptly postponed indefinitely.

Sen. Kim Gillan, D-Billings, said they needed to be delayed until ''cooler heads prevailed.''

Legislative staff said it would cost $38,000 a day to extend the regular session into a special session, which would presumably start next week.

Every bill that has not already passed the both chambers would be effectively dead at the start of a special session, lawmakers said. Each bill would have to start back at the beginning, with a committee hearing in one of the chambers before it could advance through the whole process again.

Sen. Jim Elliott, D-Trout Creek, predicted a special session could last as long as a month.

''It is not going to be fast, and it is not going to be fun,'' he said.

House Democrats, in the minority in that chamber, tried in vain to move the main budget bills that have already cleared the Senate to the floor Wednesday afternoon, but were shot down on a series of 50-49 votes. Republican leaders have been withholding the spending bills until they get a compromise on tax cuts with Senate Democrats.

Democrats also tried to get the Senate's tax cut proposal to the House floor for a vote, but were again shot down.

Rep. Art Noonan, D-Butte, said the measures need to be debated on the floor so lawmakers can adjourn before Friday and end the ''chaos that has apparently taken hold.''

Each side said the other was responsible for the impasse. Republicans said Democrats need to adopt some of the GOP's ideas for permanent property tax relief.

Lange stood up on the floor to reject any notion of bringing the budget bills forward.

Democrats want to ''just rubber stamp the governor's budget, throw some more money in it and go home,'' he said. ''Right now we don't have good-faith bargaining, we have what is an impasse.''

House Minority Leader John Parker, D-Great Falls, said there is still a small chance lawmakers could reach an agreement Thursday and rush through the remaining spending bills, along with a tax cut compromise, before Friday night.

But he didn't sound hopeful.

''We're right on track for a special session,'' Parker said.