The powerful head of the Maryland Senate warned Tuesday that because of an impasse in budget negotiations, the General Assembly may have to extend its scheduled April 9 adjournment for the first time in two decades.

Maryland Senate President Thomas V. "Mike" Miller Jr. (Patrick Semansky/Associated Press)

Under state law, the General Assembly is supposed to pass a budget by Wednesday, but negotiations between the Senate and House of Delegates has routinely pushed a final vote on the plan to the last day or two of the legislature’s 90-day session.

The most recent time the General Assembly extended a session was in 1992. But Miller has warned many times since then of another.

House lawmakers shrugged off Miller’s comment, saying it appeared he was posturing to pass the budget quickly so there would still be time before Monday for lawmakers to focus on his other favored bills, including a measure to add a new casino in Prince George’s County.

Miller, however, has leverage of his own. The fate of several bills sought by Gov. Martin O’Malley (D), including a proposed subsidy for offshore wind development, and a doubling of the flush tax to fund wastewater improvements for the Chesapeake Bay have yet to pass his chamber. Hundreds of bills sought by House lawmakers also remain to be voted on by the Senate.

House and Senate budget negotiators began meeting Monday to iron out differences in their competing $36 billion spending plans.

The two sides agree in principle: Both houses have voted to continue funding education at record levels and to raise taxes rather than cut projected spending increases that outpace still-depressed state tax revenue.

How they get there is the question.

The Senate version would collect most of its new revenue from an across-the-board income tax increase; the House version would target the top fifth of state tax filers, or most of those earning more than $100,000.

The plans also differ in how quickly they shift part of the financial burden of teacher pensions from the state to counties — a long-festering issue in Annapolis that could be on the brink of resolution.