House Republicans face a major test this week as they work to unify their diverse and narrow caucus around a plan to support President Donald Trump's agenda for trillions in tax cuts and new spending on defense and border security.

With a 218-215 majority in the House of Representatives, Speaker Mike Johnson can afford to lose just one vote on any measure that all Democrats vote against. He faces resistance from as many as a dozen Republicans over a budget resolution that would allow congressional committees to begin crafting full-scale legislation to enact the Trump agenda.

The House resolution calls for $4.5 trillion in tax cuts, which some lawmakers view in the context of the nation's $36 trillion debt. It also includes $2 trillion in spending cuts, raising concerns among some lawmakers about potential impacts on key services for constituents.

"What could go wrong, right?" Johnson joked during an appearance before the Conservative Political Action Conference last week.

"But everybody - everybody - is committed to delivering the America First agenda, and that's why we're going to get it done," said Johnson, of Louisiana.

Republicans in both the House and Senate need to pass the measure to unlock a key part of their strategy: a parliamentary tool allowing them to circumvent the Senate filibuster and opposition from Democrats.

But that is only one feat awaiting lawmakers over the coming weeks. Congress also needs to avert a partial government shutdown after March 14, when funding runs out and then raise the nation's debt ceiling or risk a default at mid-year.

Trump has gained strong support from congressional Republicans, notably by securing Senate approval for all his Cabinet nominees, including figures such as Health and Human Services Secretary Robert F. Kennedy Jr., who has expressed skepticism about vaccines, and Tulsi Gabbard, his director of national intelligence, whose past statements have raised concerns about her stance on U.S. adversaries.

House Republicans have not yet reached a consensus on the plan, despite support from the ultraconservative House Freedom Caucus, a group of about three dozen hardliners whose demands have historically posed challenges for House speakers over the past decade.

The Freedom Caucus embraced the resolution after the House Budget Committee increased the target for spending cuts from $1.5 trillion to $2 trillion while preparing the resolution for a floor vote this week. The change has raised concerns among other Republicans over a clause that calls for tax cuts to be pared back to compensate for any shortfall in spending cuts.

The higher target for spending cuts has raised concerns among lawmakers who worry about the impact on food assistance, education grants and the Medicaid health insurance program for the poor, especially for Hispanic communities that helped give Republicans their trifecta of control over the White House and both chambers of Congress.

"Some members are between undecided and 'lean no' on the resolution. Many of us still need clarity from leadership on where these savings will be coming from," said Representative Nicole Malliotakis, one of eight Republicans who expressed their concerns to Johnson in a Feb. 19 letter.

"I need answers to some questions about how we're going to achieve that without hurting Medicaid populations. That's kind of where I'm at," Malliotakis, of New York, said in an interview.

She said she would like to see savings from billionaire Elon Musk's Department of Government Efficiency, or DOGE, put toward the spending cut target as a way of protecting services to her constituents.

Trump has added complexity to the situation by suggesting he might allocate 20% of any funds saved through Musk's efforts directly to Americans.

Johnson discouraged the idea during his CPAC appearance, saying: "Fiscal responsibility is what we do as conservatives. That's our brand. And we have a $36 trillion federal debt ... I think we need to pay down the credit card."

Johnson's conference also remains vulnerable to potential infighting over other hot-button issues including a proposed increase in the federal deduction for state and local taxes and fiscal mavericks who could demand higher cuts in spending.

"Almost no one in Congress is serious about cutting spending. They're cowards," Representative Thomas Massie, an independent fiscal hawk and Johnson critic from Kentucky, lamented on the social platform X last week.

Doubts about House Republicans' unity prompted Senate Republicans to enact their own budget resolution as a Plan B ploy last week: a $340 billion measure that covers Trump's border, defense and energy priorities but leaves the issue of tax policy for later in the year.