The Patrick administration is telling executive branch agencies they should prepare for an 8 percent spending cut in fiscal 2010, which starts next July.

One source told me that Leslie Kirwan, the governor’s secretary of administration and finance, used the 8 percent figure in a budget meeting with county sheriffs today. The source said that Kirwan, preparing for the release of the governor’s fiscal 2010 budget in January, stressed that the new spending reductions would come on top of cuts already ordered to balance this year’s spending plan.

Cyndi Roy, Kirwan’s spokeswoman, declined to provide any details.

“We are beginning conversations with all agencies, including the sheriffs, about their budgets for FY10,” Roy said in an email. “It’s too soon to say, however, what those budgets will ultimately look like.”

Until now, the Patrick administration has focused on bringing this year’s $28.2 billion budget into balance. Last month, the governor announced a plan to close an estimated deficit of $1.4 billion by cutting spending and tapping the state’s rainy day reserve fund. Spending cuts totaled more than $900 million, or about 3 percent of the overall spending plan.

Kirwan’s comments today indicate the cutting is far from over. With the economy sliding into recession, the administration is apparently contemplating even bigger cuts in next year’s budget.