President Obama’s $447 billion jobs plan got generally good reviews from economists on Friday, though several noted one glaring omission: The plan does not include a comprehensive way to address mortgage debt, which many see as the central drag on the U.S. economy.

Before a joint session of Congress on Thursday night, Obama called on lawmakers to immediately pass his jobs package, which includes tax cuts for workers and employers and direct spending on schools, roads, airports and railways, among several other initiatives.

The plan — for the most part — is a conventional stimulus, much like the one passed at the beginning of the president’s term. It is designed to put more money into people’s pockets and spur hiring over the next two years, all part of an effort to stimulate spending and reduce the unemployment rate. Many economists agreed that, if passed, it would do just that.

But a contingent of economists said a conventional stimulus is not the best prescription for what ails the economy. These economists say that while a stimulus can help, the main problem is the overhang of mortgage debt created by the housing bubble that was at the center of the financial crisis of three years ago.

Americans, millions of whom owe more on their mortgages than their homes are worth, are still paying off that debt. Without a plan to reduce that debt, these economists warn, all stimulus can provide is temporary relief.

“Once stimulus fades away, households are back on the street,” said Atif R. Mian, an economist at the University of California at Berkeley. But he added, “Once you have removed the debt burden from households, you’ve taken care of the problem.”

The Obama administration says it is continuing to work on a plan to reduce the mortgage burden homeowners face each month — in particular by working with federal housing regulators to support more mortgage refinancings. But administration officials have rejected big proposals to cancel mortgage debt for fear of rewarding mortgage holders who borrowed far beyond their means.

Economists who strongly support Obama’s jobs plan agree that household debt still poses a serious problem. But they say the jobs plan will do quite a bit of good on its own.

The forecasting firm Macroeconomic Advisers said in a report that Obama’s plan — the American Jobs Act — would boost economic growth by 1.3 percentage points in 2012 and lead to 1.3 million new jobs.

Joel Prakken, chairman of the firm, said that, over several years, the stimulus would provide a temporary boost to the economy — but a boost at a time when it’s desperately needed.

“The economy’s weak now, so you want more job creation and spending now,” he said.

However, Prakken expressed some skepticism about one of the tenets of the plan, a proposal that would eliminate the 6.2 percent payroll tax on up to $50 million in new wages at a given company.

“You could either hire people or increase pay. At one extreme you might not hire anybody and just give out nice bonuses. On the other you might hire a lot of people,” Prakken said. “It’s really hard to feel confident in what incentives that will be.”

Mark Zandi, an economist with Moody’s Analytics, was even more enthusiastic about the plan. He said the jobs package would increase economic growth by 2 percentage points in 2012 and add 1.9 million jobs.

But Zandi said that when the stimulus ended, the economy would slow and the nation would still face the same level of unemployment in 2014 that it would have otherwise — 6.4 percent.

“It’s not about making the economy ultimately bigger,” he said, but “trying to alleviate the pain in the job market and the pain in the economy, and secondly, this may be more important, buying insurance to insure we don’t get back into recession.”

Peter Diamond, an MIT economist who Obama had nominated for the Federal Reserve for his expertise on long-term unemployment, credited the plan with trying to overhaul the way the nation’s unemployment machine treats job training.

Obama’s plan would allow unemployment benefits to pay for training to make it easier for the unemployed — especially those who haven’t had jobs for more than six months — to find work.

“The president did recognize that there’s a real role in increased job training and a real role for experimenting in different ways and getting a better idea of what works and what doesn’t,” Diamond said.