Originally Published: 14 JUN 21 11:42 ET

Updated: 14 JUN 21 11:51 ET

By Lauren Fox, CNN

(CNN) -- As the bipartisan group continues to educate their respective members on their $1.2 trillion infrastructure proposal, Democratic leadership and key chairs will crank up the work on a potential Democratic-only infrastructure bill this week, paving the way for Democrats to go it alone if they choose to do so.

This week, Majority Leader Chuck Schumer will meet with key members of the Senate Budget Committee including Chairman Bernie Sanders, a Vermont independent senator who caucuses with the Democrats, to begin discussions about how to effectively write and pass a budget that can pass a diverse swath of the caucus in committee.

The budget document is the first step in the reconciliation process and sets the guardrails of what any infrastructure bill can include. The budget would provide a dollar amount for each committee to spend and those targets would give instructions to key committees to rewrite the tax code and reimagine the country's social safety net in an infrastructure bill.

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Making sure the legislation would qualify under reconciliation is important because that process requires a simple majority of senators to pass, as opposed to most other legislation that needs 60 votes to advance. With the Democratic caucus in control of only 50 seats, reconciliation offers them an opportunity to pass certain legislation without Republican votes.

Aides familiar with the plans tell CNN that the bipartisan track and budget reconciliation track can work in tandem and that even if Democrats and Republicans were able to come together on a modest, bipartisan infrastructure package -- a framework for which was unveiled last week -- there still would likely need to be a path for reconciliation in order for Democrats to pass more sweeping reforms and tax changes that are a centerpiece of Biden's legislative agenda.

This budget process is expected to be far more fraught than the one that unfolded when Democrats passed the Covid-19 relief bill earlier this year, sources say. As one Democratic source told CNN, "every Democratic priority from the last 40 years is about to have to be squeezed into one bill."

The budget will only provide a framework for a Democratic-only infrastructure bill. However, in order to ensure the committees have enough flexibility, Democratic leaders have to think ahead as to what they will want to eventually include in an infrastructure bill to set the right targets. The goal is to pass the budget next month.

Still undecided is how and whether Democrats will include an overhaul of how prescription drugs are paid for in this proposal, how large of a bill Democrats can actually support and what kinds of changes to the country's policies on climate change and the care economy can actually be made under the strict budget process. Democrats will also decide how much they want to gut the Republican's 2017 tax bill in order to pay for their proposal.

One of the challenges will be that Democrats will be governed by a strict set of rules on what they can and cannot include in reconciliation. Some of those questions won't be answered for weeks, which is why aides say it is important for committees to begin the work now. Questions remain for example about whether you could include a permanent expansion of the child tax credit or a robust overhaul of the paid family leave policy on private companies.

The Finance Committee and the Committee on Health, Education, Labor & Pensions are expected to receive a large chunk of the responsibility in writing the Democratic-only infrastructure bill, sources say.

Democrats won't be able to go alone, however, until and only if moderate members agree to that process -- most notably Democratic Sens. Joe Manchin of West Virginia and Kyrsten Sinema of Arizona. That still has to play out.

But, several Democratic aides tell CNN that the effort on infrastructure is so complicated that committees have to begin their work now in order to be prepared if that eventuality comes to pass.

"The complicated factor right now is you have to let this play out," one Democratic aide said. "Members have to come to conclusions themselves."