BOSTON -- At a hearing featuring generous support for Gov. Deval Patrick's transportation-spending plan, Sen. Brian Joyce, D-Milton, uttered a note of caution about the affordability of the governor's 10-year, $19 billion construction program.

"We must have a meaningful opportunity to review what the Commonwealth can prudently afford before we take on the very significant additional debt proposed by the administration," Joyce told the Joint Committee on Transportation on Monday. He said, "I find it hard to believe that these ambitious proposals will fit within the current debt-affordability policy."

Noting payments on Patrick's proposal would extend until 2053, Joyce said he does not "sense support within the Senate to increase the statutory debt limit, particularly when our state already has among the highest levels of debt, if not the highest level of debt of any state in the nation."

Joyce said he is awaiting a report from a new Capital Debt Affordability Committee, which is due Sept. 10, and said the 2009 transportation-reform law required the Massachusetts Department of Transportation to have an integrated asset-management system, but there are still dozens of separate systems. The committee is still awaiting some appointees and has not held its first meeting, according to Joyce.

Administration officials, who are pushing a plan to generate $1.9 billion in new tax revenues, said the proposed debt is affordable and sustainable.

They said transportation reforms had saved the state $500 million, with future savings in health care still in the works.

"The policy is straightforward. It is that we will not borrow any more money than we can afford to pay debt service on," said Scott Jordan, deputy secretary for capital finance and intergovernmental affairs. Jordan said debt service could not exceed 8 percent of budgeted revenue. "All of the bond bills that we've introduced over the last several weeks all fit within that 8 percent threshold."

Joyce claims proposed bonding by the administration exceeds the amount of debt the Commonwealth is legally allowed, saying state laws allowed the state to carry $17.07 billion of direct debt at the end of fiscal 2012, of which $16.7 billion is already committed.

The committee convened to hear testimony on a bond bill that would spend $19 billion over 10 years. While it was not a direct subject of the hearing, spending on transportation construction is contingent of Patrick's plan to raise $1.9 billion annually to fund transportation and education.

Though legislative leaders have reported displeasure with tax-hike plans from constituents, and groups opposed to the new revenue have mobilized against the plan, Joyce's testimony constituted the biggest criticism of the proposal. Despite his reservations Joyce did not completely disapprove of the overall plan of raising new revenues for transportation.

"First I want to applaud the administration's initiative to address our longstanding transportation and infrastructural needs," Joyce began his testimony. "But as Senate chair of the Committee on Bonding, Capital Expenditures and State Assets, I also want to express some serious reservations concerning legislation before you today."

House Transportation Chairman William Straus, D-Mattapoisett, said he thought the committee's bonding proposal would be "safe" as long as it "matches up" with the amount of new revenue, though that number has not been determined yet.

"I think we're much closer," said Straus. Speaking about the legislative process that precedes a finished bill on Patrick's desk, Straus said, "I think there's going to be a lot of movement back and forth."

"We need to balance the costs, the debt we're going to incur and the investments we need to make with what are the larger costs of doing nothing," said Senate Transportation Chairman Thomas McGee. He said, "The tough questions need to be asked if we want to do this right, because we all need to be engaged in the solution for the future."

At Monday's nearly four-hour meeting, support for the bond bill arrived from environmental groups, business groups, and organizations representing those who would more directly benefit from the new spending: construction workers, engineers, bus drivers and bicyclists.

"I know a little something about politics," said George Bachrach, president of the Environmental League of Massachusetts and a former state senator. "What breeds cynicism is when government keeps kicking the can down the road."

Sen. Will Brownsberger, D-Belmont, asked his colleagues to keep in mind the importance of MBTA maintenance, which he said is sorely needed to reduce congestion in the transit system. A bicyclist himself, Brownsberger said it is faster to bicycle to Boston College than it is to take the Green Line.

Rep. John Fernandes, D-Milford, asked Brownsberger, who discussed the Longwood Medical area in particular, whether businesses in his district would be willing to pay a surcharge based on the number of employees, and whether riders would be willing to pay increased fares.

"Most of these institutions would say, 'We're already doing that. We are already contributing substantially to the MBTA revenue stream by paying for our employees' passes,' " Brownsberger said.

"There has been some discussion about employer surcharges," Fernandes said.

Leaving aside the question of its size and how it is funded, Straus said that a transportation bond bill will reach the governor's desk.

"There will be a transportation bond bill approved by the Legislature," said Straus. "That I know. What is left is: What are the details, and what is the time-period and scope of the legislation itself?"