Nobody knows exactly what will be aboard the omnibus. But everybody is aware of the fact that it will likely be loaded down with a lot of last-minute surprises.

“Early on I asked that if that was going to happen, that I be advised,” House Appropriations Chairman Bill Young (R-Fla.) said of the expected legislative add-ons. “I haven’t been advised on any yet, but that doesn’t mean there won’t be some.”

Senate Appropriations Chairman Ted Stevens (R-Alaska) echoed that sentiment.

“I have no directions yet [from Senate Republican leaders],” Stevens said. “But it’s hard to give appropriators directions because there are so many issues.”

Indeed, the wish list so far is long and varied.

“Everybody who has a bill that is in any trouble at all is talking about putting it on the omnibus,” noted Sen. Bob Bennett (R-Utah), who chairs the Senate Appropriations subcommittee on Agriculture and whose measure is likely to be used as the vehicle for the five- or six-bill omnibus.

Potential legislative add-ons to the omnibus — or “minibus,” as some are calling it — include several long-stalled bills, such as the Federal Aviation Administration authorization, a measure to ban taxes on Internet hookups and a pension-funding bill.

The reauthorization of the Fair Credit Reporting Act as well as a bill to authorize Army Corps of Engineers water resources projects could also end up taking rides on the omnibus.

House and Senate GOP leaders also have discussed adding President Bush’s “Healthy Forests” wildfire prevention bill to the omnibus, if it appears there is not enough time to consider a conference report before adjournment. Still, House and Senate aides on Wednesday said the current plan was to try to move the forest bill as a stand-alone measure.

Other smaller projects are also up for consideration as riders.

Sen. Chuck Grassley (R-Iowa) may push his proposal to provide federal help to build an environmental tourist attraction, including an indoor rain forest and aquarium, in Coralville, Iowa. Grassley lost in his first attempt to get the provision attached to the energy policy measure, after House negotiators balked at what they said was a special-interest provision for Iowa.

As was the case last year, Young noted that the national flood insurance program would have to be reauthorized in the omnibus because, he said, “the authorizers just didn’t get around to extending it, so we’re going to have to deal with it.”

A provision to prohibit the Federal Communications Commission from auctioning off a portion of the radio spectrum currently reserved for satellite communications could also show up on the omnibus. The provision is intended to carve out part of the satellite communications spectrum for use by land-based wireless companies, and if adopted it would primarily benefit Northpoint, a small telecommunications company.

Sen. John McCain (R-Ariz.) strongly opposes the Northpoint language and has threatened to hold up consideration of the omnibus if it — or any other major legislative language — is included in what is supposed to be strictly a spending bill.

“We hear, and I don’t know if it is true or not, that there are a number of policy changes ranging from Northpoint to media ownership to fishing. And obviously I don’t believe those major policy issues should be part of appropriations bills,” McCain said Tuesday.

McCain added: “I spoke at the [GOP policy] lunch today, and I said, ‘Look, everybody wants to get out of here and I want to get out of here, but if there is an omnibus bill that is crammed full of policy changes we are going to spend a long time’” on the Senate floor debating it.

A Senate GOP leadership aide acknowledged that McCain’s threat would cause problems for the ultimate passage of the omnibus, but said the Senator would not stop Republican leaders from moving forward with an omnibus spending measure that includes a variety of policy add-ons.

“There’s not enough grease for all the squeaky wheels,” the aide explained.

However, Members are mindful that major controversies cannot be attached to the omnibus.

“We don’t want to put anything on there that could jeopardize [passage of] the omnibus. So it’s got to be all resolved beforehand,” explained Senate Republican Policy Committee Chairman Jon Kyl (R-Ariz.).

Kyl said GOP leaders were very interested in including a bill to prohibit states and localities from taxing Internet broadband hook-ups.

However, the bill’s primary proponent, Sen. George Allen (R-Va.), has not been able to forge an agreement on the bill’s language with the chief opponent of the legislation, Sen. Lamar Alexander (R-Tenn.). Without an agreement between the two sides, the bill will have to wait until next year, according to Kyl.

Kyl also noted that a number of laws that would otherwise expire at the end of the year will likely have to be attached to the omnibus, including a variety of tax credits.

The pension-funding issue also must be dealt with before the end of the year, because the current formula companies use for funding their employee pension plans expires at the end of December.

Senate Republicans also are divided on whether to give in to Democratic demands that they extend unemployment insurance that will expire at the end of the year, according to a Senate GOP leadership aide. If they agree to extend unemployment aid, it could be attached to the omnibus.

Meanwhile, both House and Senate appropriators are bracing for a potential onslaught of requests for additional spending on the omnibus, particularly once House GOP leaders finish all the horse-trading they’re expected to do in order to secure enough votes for the Medicare prescription drug conference report.

Young said getting Members to vote for something they would otherwise oppose usually involves promises of more money for funding projects in their districts. If House GOP leaders agree to a number of those spending increases, appropriators will have to scramble to find offsets.

“We’re not going to go above the budget caps,” Young explained.

But Young’s biggest complaint was that the legislative riders originally included in several of the already passed spending bills are holding up appropriators’ ability to begin serious negotiations about what should go into the omnibus.

“It’s always the non-appropriations issues that cause us the most trouble,” said Young, speaking specifically of wrangling over provisions that would overturn administration overtime pay rules, attempts to weaken administration plans to outsource some federal jobs, and provisions to prohibit the FCC from implementing new media ownership rules.

Mark Preston contributed to this report.