Congress’ September agenda is packed with several must-pass bills that Republicans and Democrats are likely to look to as leverage for extracting concessions on other priorities.

With a short legislative calendar next month — only 12 days when both chambers are scheduled to be in session (the Senate has a few extra days on its timetable) — some measures could be packaged together, creating even more leverage and risk.

Atop the to-do list is funding the government by Sept. 30, the end of the fiscal year, and raising the debt limit by Sept. 29, when the Treasury Department estimates the government would be in danger of defaulting on its borrowing obligations.

Republican leaders have promised to address both issues prior to the deadlines but have not specified their plans for doing so.

“Talks continue with our counterparts in the Senate and the administration, and we will act before the deadline,” said Doug Andres, a spokesman for House Speaker Paul D. Ryan.

Treasury Secretary Steven Mnuchin has called on Congress to pass a “clean” debt limit increase, meaning one that’s free of partisan policy riders. But conservatives have balked at the idea, saying any increase should be attached to legislation that addresses deficit spending.

“The debt ceiling increase needs to be accompanied by reforms to address the problems that cause it,” Republican Study Committee Chairman Mark Walker said in an op-ed earlier this month in The Washington Examiner. “We can’t afford to kick this can down the road. Otherwise, Republicans lose credibility the next time we point out (as we often do) that the national debt is a serious problem.”

Walker said a clean debt ceiling increase appears to lack the needed support, increasing the likelihood that “congressional leaders load it up with even more increased spending and must-pass legislation to attract the necessary votes.”

“Historically, this is done by reaching across the aisle to produce a bill that is as unsavory politically as it is fiscally,” the North Carolina Republican added.

Outside conservative groups are also opposed to a clean debt ceiling increase.

Jason Pye, vice president of legislative affairs for FreedomWorks, said his group is still formulating specific asks but noted that any increase should be paired with “spending reductions or some sort of re-prioritization of payments.”

Not addressing spending alongside the debt limit would send a terrible message to conservative grass-roots activists, especially after Congress failed to repeal the 2010 health care law, Pye said.

“I think that will infuriate them to be honest with you,” he said.

Given the conservatives’ position against a clean debt limit increase, GOP leaders would need a lot of Democratic support if they tried to push one through.

A House Democratic leadership aide said there’s been no outreach from the Republicans or the White House on the debt ceiling or an appropriations package for funding the government. It’s likely that a debt limit increase would be attached to the spending bill, the aide said.

The spending bill, which could be a 12-bill omnibus or a continuing resolution if talks break down, has its own pressure points.

Republicans are pushing for funding to begin construction of wall or fence along the southern border, one of President Donald Trump’s key campaign promises.

Democrats, however, have warned that’s a nonstarter. Any GOP effort to leverage the debt ceiling or the renewal of aviation, children’s health insurance and flood insurance programs to extract border wall funding will be met with fierce Democratic opposition.

“These are items that the American people expect us to address — not opportunities for Republicans to hold government hostage for poison pill provisions, such as funding for an ineffective border wall,” House Minority Whip Steny H. Hoyer said in a statement to Roll Call about the September must-pass bills. “Forcing American taxpayers to foot the bill for the wall is not must-pass legislation and shouldn’t be tied to any of these issues.”

Trump, however, has signaled that he’s not planning to lose another fight over money for the wall after conceding to Democratic demands to exclude such funding from the delayed fiscal 2017 omnibus Congress passed in May.

At the time, the president blamed the loss on the Senate’s filibuster rule, suggesting an end to the 60-vote threshold for legislation and threatening disaster if he didn’t get his way.

“Our country needs a good ‘shutdown’ in September to fix mess!” Trump tweeted in May.

GOP leaders have tried to quash any rhetoric regarding a shutdown, knowing their party will likely be blamed if one were to occur.

But the path to avoiding a shutdown is murky since border wall funding is just one issue that needs resolved.

Before wading into the fight over partisan riders, party leaders first need to agree on topline spending levels. Republicans want to significantly increase defense spending and Democrats have said any defense boost should be matched by a corresponding domestic spending increase. If lawmakers want to increase spending beyond the sequester caps, Congress first needs to pass legislation making those changes.

Since negotiations over the budget caps have not really started as yet, lawmakers and aides on both sides of the aisle are predicting a short-term continuing resolution will be needed to avoid a shutdown and buy more time for an omnibus agreement.

Increasing the debt limit and funding the government are the two major hurdles that Congress must overcome this September but they’re not the only ones.

Authorizations for the Federal Aviation Administration, the Children’s Health Insurance Program and the National Flood Insurance Program are all scheduled to expire Sept. 30 absent congressional action.

House and Senate committees of jurisdiction have been working on packages that would both reauthorize and overhaul these programs, but with a short calendar and contentious proposals to work through, Congress may punt on the larger measures and just pass-short term reauthorizations.

CHIP, which helps states provide health care access for poor children whose families do not directly qualify for Medicaid, has bipartisan support but is typically a higher priority for Democrats than Republicans.

Since the Republicans’ failure to repeal and replace the 2010 health care law, some lawmakers have discussed using the CHIP reauthorization as a vehicle for policy changes needed to help stabilize the health insurance market.

Some Senate aides have said CHIP could be used as a medium for raising the debt ceiling.

The House and Senate have prepared different FAA reauthorization proposals but neither chamber has brought legislation to the floor.

The House bill, which would move FAA air traffic control into the hands of a nonprofit corporation, appears to lack the votes to pass amid Democratic and Republican opposition.

Adding a more popular measure to the FAA reauthorization may make it an easier pill to swallow but more likely would doom any must-pass item that got rolled into it.

“I don’t know what changes you can make to that bill to make it more palatable,” FreedomWorks’s Pye said.

A larger overhaul of the flood insurance program could get bogged down amid disagreements over a GOP proposal to allow more private insurers to provide coverage options and a Democratic proposal to add $1 billion for mitigation programs.

With controversy over competing priorities surrounding all five must-pass bills on Congress’ September agenda, it’s almost certain there will be strong arming and horse trading. What’s uncertain is which side will emerge as the winner, or if both parties will lose in failing to meet these critical deadlines.

Joe Williams and Doug Sword contributed to this report.Get breaking news alerts and more from Roll Call on your iPhone or your Android.