WASHINGTON — The June 1 "X date" is approaching, the earliest the U.S. government could run out of money to pay its bills if leaders do not reach a deal to lift the debt limit.

After that date, the Treasury will have to decide which obligations don't get paid, even as multiple critical bills are due.

Lifting the debt ceiling is necessary for the government to cover spending commitments already approved by Congress and the president — and prevent default. Doing so does not authorize new spending. President Joe Biden is currently in a standoff with House Speaker Kevin McCarthy, who has refused to raise the debt limit if Biden and lawmakers do not agree to future spending cuts. McCarthy said he hopes the House will vote on a debt limit bill as soon as next week.

The think tank Bipartisan Policy Center modeled the Treasury Department's cash flow, noting what day bills are paid. The schedule offers a look at the government's spending priorities as it approaches June 1.

The Treasury has taken extraordinary steps to keep paying the government's bills, and expects to be able to avoid a first-ever default at least until early June. Treasury Secretary Janet Yellen demurred when asked in an interview with CNBC this month what bills would be prioritized in the event of a default.

Here's a look at the bills that come due in the first half of June, according to analysis from the Bipartisan Policy Center based on daily and monthly Treasury statements. Only the major spending categories are outlined, meaning the numbers may not add up to the total spending due that day.

June 1: $101 billion in spending due; estimated $26 billion in revenue

Medicare: $47 billion

Veterans benefits: $12 billion

Military pay and retirement: $10 billion

Civil service retirement: $6 billion

June 2: $40 billion in spending; $18 billion in revenue

Social Security benefits: $25 billion

Medicaid: $2 billion

Education programs: $1 billion

June 5: $13 billion in spending; $33 billion in revenue

Medicare: $1 billion

SNAP benefits: $1 billion

Defense vendor payments: $1 billion

June 6: $17 billion in spending; $15 billion in revenue

Medicaid: $6 billion

Defense vendor payments: $2 billion

Education programs: $1 billion

June 7: $16 billion in spending; $18 billion in revenue

Defense vendor payments: $2 billion

Transportation programs: $1 billion

Individual tax refunds: $1 billion

June 8: $18 billion in spending; $13 billion in revenue

Medicaid: $6 billion

Defense vendor payments: $2 billion

Education programs: $1 billion

June 9: $21 billion in spending; $18 billion in revenue

Federal salaries and insurance: $5 billion

Medicaid: $5 billion

Education programs: $1 billion

June 12: $23 billion in spending; $33 billion in revenue

Pension Benefit Guaranty Corporation: $7 billion

Federal salaries: $2 billion

SNAP benefits: $1 billion

June 13: $15 billion in spending; $15 billion in revenue

Defense vendor payments: $3 billion

Medicaid: $2 billion

Medicare: $1 billion

June 14: $38 billion in spending; $37 billion in revenue

Social Security benefits: $25 billion

Individual tax refunds: $1 billion

Medicaid: $1 billion

June 15: $22 billion in spending; $79 billion in revenue (quarterly tax receipts are due)

Military salaries: $4 billion

Medicaid: $3 billion

Interest on public debt: $2 billion

June 16: $12 billion in spending; $29 billion in revenue