While U.S. lawmakers managed to avoid going over the fiscal cliff, Moody’s Investors Service says that the agreement still doesn’t provide a basis for a meaningful improvement in the government’s debt ratios over the medium term.

The rating agency said Wendesday it expects that further fiscal measures are likely to be taken in coming months that would result in lower future budget deficits, which are necessary if the negative outlook on the government’s bond rating is to be returned to stable. “On the other hand, lack of further deficit reduction measures could affect the rating negatively,” it says.

Moody’s notes that yesterday’s package does not address the federal government’s statutory debt limit, which was reached on December 31. “The need to raise the debt limit may affect the outcome of future budget negotiations,” it notes.

While the fiscal package raises some revenue through higher tax rates on high earners, Moody’s says “the estimated amount of increased revenue over the next decade is far outweighed by the amount of revenue foregone through the extension of lower tax rates for those with incomes below $400,000, the indexation of the alternative minimum tax, and other measures.”

Moody’s estimates that the ratio of government debt to GDP would peak at about 80% in 2014 and then remain in the upper 70% range for the remaining years of the coming decade. “Stabilization at this level would leave the government less able to deal with future pressures from entitlement spending or from unforeseen shocks. Thus, further measures that bring about a downward debt trajectory over the medium term are likely to be needed to support the Aaa rating,” it says.

Additionally, the rating agency notes that the macroeconomic effects of the package are positive, “since it averts the recession that would likely have occurred had personal income taxes gone up for all income levels”. However, it adds that the increase in the Social Security payroll tax will likely be a constraint on growth in coming quarters. And, spending cuts that may be decided in coming months could also affect the rate of GDP growth in the near term, it says.

“Overall, therefore, the recent package mitigates part of the fiscal drag on the economy associated with the fiscal cliff but does not eliminate it,” it concludes.

Moreover, the debt limit will have to be raised in February or early March, it says, adding, “… it seems likely that new measures addressing the expenditure side of the budget will be negotiated at around the time the debt limit will need to be raised.”

Although Moody’s says it believes that the debt limit will eventually be raised and that the risk of default on Treasury bonds is extremely low, “this confluence of events adds uncertainty to the outcome of negotiations,” it adds.

“The debt trajectory resulting from this process is likely to determine whether the Aaa rating is returned to a stable outlook or downgraded to Aa1,” Moody’s says.