WASHINGTON — Senate Republicans have issued a series of early threats against a still-forming deal to fund the federal government, signaling that they could delay the package – which may include emergency aid to Ukraine – over concerns about excessive spending and vaccine mandates.

The early warnings, delivered in two letters to Senate Majority Leader Chuck Schumer, D-N.Y., could slow lawmakers’ time-sensitive work at a moment when Russia’s incursion into Ukraine is intensifying – all while Washington faces a March 11 deadline to fund federal agencies and avoid a government shutdown.

In the first letter, sent Thursday, eight GOP lawmakers complained that “families are feeling the pressure of skyrocketing prices,” which they blamed on “reckless government spending.” In response, they said they “cannot allow another massive spending package to be rushed through Congress without proper consideration and scrutiny.”

Sen. Ted Cruz, R-Texas, and seven other GOP lawmakers say they “cannot allow another massive spending package to be rushed through Congress without proper consideration and scrutiny.” Andrew Harnik/Associated Press, file

The letter demanded “appropriate time” to read and review any funding bill. It also called for an official analysis by the Congressional Budget Officeto assess the impact of the legislation on inflation and the federal debt. And it signaled that Senate Republicans could withhold their votes if their terms are not met, potentially slowing debate to a crawl.

“Until we can fully understand what is in any potential (spending) bill, its impact on the fiscal strength of the United States, and how it will influence our nation’s growing inflation crisis, we should not vote on it,” they wrote.

Signing the missive were Republican Sens. Rick Scott of Florida; Cynthia Lummis of Wyoming; Ted Cruz of Texas; Roger Marshall of Kansas; Marsha Blackburn of Tennessee; Mike Braun of Indiana; Ron Johnson of Wisconsin; and Mike Lee of Utah.

In the second note, sent Friday, 10 Republicans revived their campaign against federal vaccine and testing requirements. Even as public health officials broadly maintain the policies help curtail the spread of the coronavirus, the GOP lawmakers pledged they would “stand against these mandates until they are discontinued in ambition, design and practice.”

Specifically, the Republicans promised to block lawmakers from forging ahead swiftly to pass the bill if it funds implementation of mandates. They said “at the very least” they would “require a roll-call vote on an amendment that defunds enforcement,” a move Republicans have demanded in other recent government funding fights.

The second missive was signed by some of the same Republicans, plus Sens. Rand Paul of Kentucky and Steve Daines of Montana.

While it is unclear how far Senate Republicans might take their latest threats, their twin missives added to the challenges facing congressional leaders as they seek to cobble together a long-term government funding deal, a goal that has eluded them for months. Both sides insist they do not want a shutdown, though their bickering – intensified by GOP demands – repeatedly has pushed the country to the brink over the past year.

For now, Democrats and Republicans say they are making progress on a long-term deal, which could include massive increases in spending at key domestic agencies as well as the Pentagon. House Majority Leader Steny Hoyer, D-Md., previously has said that he hopes to hold a vote on the package, known in congressional parlance as an omnibus, as soon as Tuesday, leaving theSenate a short window to act before the March 11 deadline.

Their efforts have gained greater urgency as result of Russia’s intensifying invasion of Ukraine, since lawmakers in both parties see the funding measure as an opportunity to deliver billions of dollars in new humanitarian and military assistance. Senior administration aides this week requested about $10 billion in emergency funding for Ukraine, which some Democrats and Republicans hope to augment with further punishments against Russia, including new limits on imports of Russian oil.

On Saturday, Ukrainian President Volodymyr Zelensky addressed U.S. lawmakers via Zoom and pleaded for more assistance to his war-torn nation, according to a person familiar with the call who requested anonymity to describe the sensitive briefing. His request included the provision of additional lethal aid, as well as support for a global effort to stop buying Russian oil.

Exiting the call, Sen. Christopher Coons, D-Del., said Zelensky’s “call to action must lead to swift passage by Congress of the $10 billion in emergency supplemental aid.”

Cruz, Lee and some other Republicans issuing threats against the spending bill have a history of using government funding battles to advance political objectives. Recently, the duo has forced Democrats to hold a series of ill-fated votes targeting President Biden’s policies requiring coronavirus vaccines and testing, nearly pushing the government to shut down.

Scott, meanwhile, has found himself at odds in recent days with some members of his own party over his economic plan, released in February. That proposal has drawn objections from Senate Minority Leader Mitch McConnell, R-Ky., among others, and Scott on Friday fired off an op-ed in the Wall Street Journal blasting “Beltway cowardice” over government spending.

Earlier in the week, a wider array of Republicans issued the first warnings against the omnibus, telling Democrats they may not be able to support a spending deal that provides billions of dollars in fresh coronavirus aid. The lawmakers said they wanted a fuller accounting of how previous aid had been spent before considering new sums.

The Biden administration has said it needs more than $22 billion to prepare for future waves of the pandemic.