If Congress decides to put together an economic stimulus package, it should be large enough to do some good - about $100 billion - and temporary, according to senators who got that advice from Federal Reserve Chairman Alan Greenspan.

In a private session Tuesday with leaders from the Senate Finance Committee, Greenspan and former Treasury Secretary Robert Rubin said the $100 billion they had in mind would include a $40 billion emergency spending plan and $15 billion in airline aid already passed, participants said.

There was agreement among Democrats and Republicans that any stimulus should be temporary, perhaps limited to a year or two, to guard against negative long-term effects such as federal budget deficits and higher long-term home mortgage rates.

``I think it has to be temporary but significant enough to make a difference,'' said Sen. Charles Grassley of Iowa, ranking Republican on the Finance Committee.

No decisions were made about which specific tax breaks to pursue or even whether to proceed with an additional stimulus plan, which Greenspan again urged should await better economic data to determine what might work.

Many Republicans, particularly in the House, are eager to move ahead with a stimulus plan as early as next week as the economy struggles in the aftermath of the terrorist attacks. Democratic leaders continue to stress Greenspan's wait-and-see approach - which is also embraced by the White House.

``I think everybody is willing to wait a week or two,'' said Senate Minority Leader Trent Lott, R-Miss. ``There's also a feeling by a lot of us that we're going to have to put a little more juice in the economy with some sort of stimulus.''

Like other Democrats, Senate Finance Committee Chairman Max Baucus said it was important to gauge the effect of these actions on the economy before taking additional steps.

``There's a lot already in the pipeline,'' said Baucus, D-Mont.

Rep. Jim McCrery, chairman of the revenue subcommittee of the House Ways and Means Committee, said the $100 billion figure ``sounds about right'' if it includes some of the previous spending action, leaving about $50 billion for tax cuts.

``We are collecting ideas, fleshing out ideas,'' said McCrery, R-La. ``We're hopeful we will be ready to move next week.''

At the White House, spokesman Ari Fleischer said whether to proceed with a stimulus plan remains under review. ``It won't be a rush to come out with an economic stimulus because the nation was attacked. It has to be done right,'' he said.

Even with the go-slow approach, there is no shortage of options suggested by Republicans and Democrats, including some spending proposals.

Republicans have focused on items such as cuts in capital gains taxes on investments, accelerated depreciation for business, more generous expensing write-offs for small business, cuts in corporate tax rates and making parts of the just-enacted tax cut take effect more quickly.

Among the Democratic ideas are an extension of unemployment benefits, temporary suspension of payroll taxes, a new round of tax rebate checks focused on those who didn't qualify for a check this summer and helping people pay for health insurance plans.