Washington is set for a rollicking tax fight in the coming year, with observers of all stripes expecting a historic deal to extend Donald Trump's 2017 tax cuts at some point.

The key question for the moment is timing, and the debate on that subject has revealed early fissures among Republicans on exactly how quickly it might be possible to hammer out a massive tax bill.

In recent weeks, President-elect Trump, along with Senate and House Republicans, has discussed whether to start the process with one or two reconciliation bills.

At the core of these talks is the question of whether it would be best to move quickly on taxes or whether drawn out negotiations will be needed that push taxes into a second bill.

House Ways and Means chair Jason Smith is the Republicans' chief tax-writer and has been calling for a single bill. He repeated his push last Tuesday during a hearing, saying "we must not leave families and small businesses waiting for Congress to do the right thing and provide tax relief at the 11th hour."

Smith's single bill strategy would pair taxes with other issues like immigration and energy where a GOP consensus is clearer. The goal there is for a massive package as soon as April.

But taxes could be a different story, with many skeptical that complex tax issues can be hammered out that quickly.

Trump himself is leaning toward the quick and sweeping action that a single bill would entail and has endured repeated lobbying on the topic -- including at least once in the middle of an interview.

"The reason I want one bill is because tax certainty matters to small business people like me and like everyone listening to this show," radio host Hugh Hewitt told the president-elect during a recent appearance.

But a single bill may not be politically possible, with an array of knotty issues still unresolved that could turn various Republicans against such a bill and imperil its chances given the GOP's ultra slim margins in the US House.

Foremost among these complications is the ballooning national debt, with questions swirling about whether it curtails Republican ambitions for tax breaks that could add new red ink atop the existing $36 trillion dollar pile.

The non-partisan Committee for a Responsible Federal Budget estimates that extending Trump's 2017 tax cuts would not pay for themselves; the Congressional Budget Office has said the tab could be $3.7 trillion in additional debt between now and 2034 unless the costs are offset.

Another key potential sticking point are certain corners of the tax code that certain groups who boast numbers big enough to sink the bill hold dear, such as the state and local tax (SALT) deduction.