BOSTON - Lawmakers were poised Monday to give final approval to a $34 billion state budget that includes additional state aid for cities and towns and enough funding for the University of Massachusetts to avoid a tuition increase in the upcoming academic year.

A six-member House-Senate conference committee quietly reached agreement on the spending plan late Sunday after several weeks of closed-door negotiations to resolve differences between versions of the budget that passed earlier in both chambers.

The House and Senate are expected to take votes on the plan later Monday, with no additional amendments allowed. The votes would come a few hours after the start of the state's new fiscal year, which began at 12:01 a.m.

The state, however, is operating on a stopgap budget and likely will continue to do so for several days while Gov. Deval Patrick reviews the spending plan and decides on which portions he will exercise his line-item veto power.

The budget calls for a $21 million hike in unrestricted aid for the state's cities and towns and a nearly $110 million increase in so-called Chapter 70 assistance for public schools.

Budget negotiators resolved one key area of difference by adopting the House appropriation of $479 million for the University of Massachusetts. The Senate had approved $455 million for the school.

The higher figure means Massachusetts students will not have to pay more next year to attend classes, university president Robert Caret said.

"The conference committee has taken a major step on the university's behalf by approving a funding increase that will allow UMass to freeze tuition and mandatory fees for in-state students, while at the same time continuing to provide the high level of academic quality that our students deserve and expect," Caret said in a statement Monday.

The budget also includes $15 million in funding for early childhood education, which, according to lawmakers, will take about 2,000 children off the waiting list for income-eligible child care.

The spending plan also adds more than $6 million to provide home care services for an additional 1,500 elderly residents.

The budget maintains 45 mental health beds at the Taunton State Hospital, despite calls from the Patrick administration to close the aging hospital and transfer patients to other facilities.

The spending plan relies in part on $500 million in new taxes that are included in a separate transportation finance bill that is now on Patrick's desk. But the governor has said he plans to return the bill to the Legislature seeking an amendment that would address the potential loss of future transportation revenue from the elimination of tolls on the western portion of the Massachusetts Turnpike in 2017.

The budget authorizes the state to tap its stabilization fund, better known as the rainy day fund, for $350 million in the new fiscal year. The fund would retain a balance of more than $1 billion after the transfer.