Some Senate Republicans are raising concerns about a provision in a mammoth stimulus package unveiled Thursday that would reduce the amount of cash assistance for lower-income individuals.

Sens. Mitt Romney (R-Utah) and Josh Hawley (R-Mo.) are pushing for changes to the provision, arguing that individuals with little or no tax liability should get the same $1,200 check that Republicans are promising for individuals who make up to $75,000.

"The current bill has promise but it shouldn't give lower earners smaller checks - that's directly contrary to my proposal. We need to fix this to ensure lower earners get equal payments," Romney tweeted on Thursday night

Hawley added that the Senate GOP bill "needs to be fixed."

"Relief to families in this emergency shouldn't be regressive. Lower-income families shouldn't be penalized," Hawley said.

Part of that plan is to give a one-time check of $1,200 to individuals who make up to $75,000. The amount received would then begin to scale down until it reached an income threshold of $99,000, where it would phase out completely. The income levels would be based on 2018 tax returns.

But a GOP summary of the bill noted that individuals with little or no tax liability would receive roughly half - a minimum of $600.

"Taxpayers with little or no income tax liability, but at least $2,500 of qualifying income, would be eligible for a minimum rebate check of $600 ($1,200 married). Qualifying income includes earned income, as well as Social Security retirement benefits and certain compensation and pension benefits paid to veterans. This ensures relief gets to low-income seniors and disabled veterans," the summary reads.

The pushback comes after Senate Majority Leader Mitch McConnell (R-Ky.) and several GOP chairmen unveiled the bill, the third package aimed at combating the impact of the coronavirus, on Thursday afternoon.

The nearly 250-page bill includes help for individuals, small businesses and industries impacted by the spread of the coronavirus and the steep economic toll it's taken thus far.

The two GOP senators have unveiled their own proposals for giving cash assistance to Americans.

Romney's proposal would give $1,000 to every American adult, while Hawley's would scale based on family size. A family of three, for example, would get $1,446, while a family of five would get $2,206.