Even as a $1 trillion price tag and partisan bickering threaten to derail Senate passage of health care reform this year, another major obstacle looms large: the merger of two competing bills by two powerful Democratic committee chairmen.

Finance Chairman Max Baucus (Mont.) and Health, Education, Labor and Pensions No. 2 Democrat Chris Dodd (Conn.) — who is pinch-hitting for Chairman Edward Kennedy (D-Mass.) — both contend that marrying their two health care bills into a single vehicle will be seamless. But last week, it was increasingly apparent that these two Senate committees are working on separate, and conflicting, tracks.

HELP on Wednesday began marking up expensive legislation that appeared geared toward satisfying liberal health care reform goals. Meanwhile, the markup of the Finance bill was delayed from its original start date of Tuesday so that Baucus could continue to pursue a bipartisan agreement on legislation that costs less than $1 trillion and is deficit-neutral.

“It’s a big challenge,— Senate Democratic Conference Vice Chairman Charles Schumer (N.Y.) said late last week when asked about the pending negotiations to merge the bills.

Schumer indicated that Majority Leader Harry Reid (D-Nev.) could be the ultimate arbiter of the Baucus and Kennedy legislation. Kennedy, absent from the Senate as he battles brain cancer, remains in constant contact with Dodd, who regularly mentions that Kennedy hopes to return in time to shepherd health care reform across the finish line.

Shuttling in and out of closed-door Finance Committee meetings last week, Baucus insisted that melding his legislation with the HELP bill would not be problematic. But Dodd’s comments on his health care reform priorities suggested that the marriage of the Finance and HELP bills is in need of some pre-emptive counseling.

“I certainly would love to have bipartisan support in the committee for the final product. But my goal here is to write a good bill; my goal is not bipartisanship,— Dodd told reporters Thursday.

That statement — and Dodd’s dismissal of the notion that any health care package should be influenced by the Congressional Budget Office’s cost calculations — directly contradicts what Baucus has said throughout the Finance negotiations.

Baucus delayed the markup of his bill because the preliminary CBO scoring of the Finance bill — well over $1 trillion — came in too pricey for his taste. But the Montana Democrat has placed particular emphasis on crafting a bipartisan bill, saying that is the best way for health reform to earn public confidence and survive long-term.

“I think it’s very important to get a good, bipartisan bill,— Baucus said.

Democrats and Republicans still vehemently disagree over whether to include a government-run insurance option as part of a health care overhaul, and the two sides remain at loggerheads over employer mandates and how to pay for reform.

The HELP Committee bill is on track to include a robust government-run option, and Dodd has said that holding down costs is important but not an overriding concern. The Finance Committee is trying to fashion a compromise on the public-plan issue that can garner the support of both sides, with Baucus taking a more cost-conscious approach.

Still, Baucus predicted that the two committees would come to an agreement on those issues.

“We’ll work it out, because we have to,— he said.

President Barack Obama has asked that a health care reform bill land on his desk no later than Oct. 15. To comply, Democratic Congressional leaders have targeted the end of July to clear bills out of the House and Senate. A conference committee would likely follow after Members return from the August recess.

But adhering to this timeline could prove difficult given the growing potential for Senate delays.

The decision by Baucus to push the markup of the Finance bill until after the July Fourth recess is just one reason. HELP is also contributing, since it had yet to finish drafting the language for its bill as of Friday despite being three days into its markup session.

And then there’s the time that will be needed to merge the Finance and HELP bills, which cannot occur until after the two have completed their respective markups. Sen. Orrin Hatch (R-Utah), a veteran lawmaker who sits on both Finance and HELP, predicted the negotiations would be tricky and that the policy differences in the two bills would be tough to reconcile.

Senate Republican Conference Chairman Lamar Alexander (Tenn.), who sits on HELP and like most of his GOP colleagues is a critic of the health care reform bill as it is shaping up there, also projected a rocky merger with Finance. Alexander said having to meld the two bills adds an additional layer to an already difficult process.

“It makes it complicated,— he said.