Montgomery County Executive Isiah Leggett is asking the County Council to trim its proposed additions to the fiscal 2014 budget, warning that excessive new spending could jeopardize progress in stabilizing the county’s finances.

Leggett added significant new costs of his own to the $4.8 billion budget he proposed for the fiscal year that begins July 1, negotiating new contracts with county employee unions that will cost more than $31 million. But in a letter released late Monday, he said the council’s amendments — which total about $18.3 million — would push spending to unsustainable levels. He said the threats posed by federal sequestration, cuts in state support and a potentially costly tax case pending in the Maryland Court of Appeals all demand caution.

“We have worked tirelessly and collaboratively to turn the county’s financial ship around, and I would urge the council not to retreat from this goal at this critical juncture,” Leggett said in the letter to Council President Nancy Navarro.

If adopted in their entirety, the council’s additions would increase spending from the 4 percent proposed by Leggett to more than 5 percent over the current fiscal year.

The letter registered barely a ripple with the council as it worked through the budget on Tuesday. Members said such cautionary messages from Leggett are a regular feature of the annual cycle.

“It’s customary,” said Navarro. “Every year the council is very mindful of expenditures and will continue to be.”

“We get something like this every year,” said Council member George Leventhal (D-At-Large)

Over the past several weeks, council members have proposed dozens of changes, including additional funds for mammograms and colorectal cancer screening, reimbursements to assisted-living group homes and medical clinics, and increased subsidies for child-care services and non-profits.

The council is also considering measures that would reduce the 2010 increase in the county energy tax by as much as 10 percent--as it did last year-- shrinking revenue by $11.6 million. There is a proposal to restore at least some of the county’s match to the state Earned Income Tax Credit for working families, which had been cut during the recession. That measure could cost anywhere from $200,000 to $1 million.

Leggett said that the salary increases he proposed (and that were approved last month by the council) are more than justified by the savings accrued from several years of pay freezes and furloughs.

In his letter, he said that the combination of new spending and reduced revenue contemplated by the council will make it more difficult to balance next year’s budget, for fiscal 2015. Early projections show a gap of about five percent between projected spending and available revenue, Leggett said.

Navarro said the council will likely winnow its wish list as it continues to work through the budget in sessions this week.

“Now it’s a matter of the dance,” she said. “How much members will be willing to compromise.”

Final action on the spending plan is expected next Thursday.