WASHINGTON — President Obama called on lawmakers Monday to back an ambitious initiative to modernize the nation’s crumbling roads, railways and airports, saying the strategy would not only improve the economy in the long run but create good jobs now.

On the heels of a report last week showing the jobless rate stuck at 9.6 percent, Obama touted his infrastructure plan as the ideal antidote, noting that unemployment is particularly high in the construction trades.

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President Obama prepares to board Marine One in Washington on Monday as he travels to Miami. “All we need is the political will” to invest in infrastructure, he said. The Associated Press

“Nearly one in five construction workers is still unemployed and needs a job. And that makes absolutely no sense when so much of America needs rebuilding,” Obama told reporters in the Rose Garden.

“Investing in infrastructure is something members of both political parties have always supported,” Obama said. “There’s no reason why we can’t do this. This is work that needs to be done. There are workers who can do it. All we need is the political will.”

The Rose Garden statement capped a series of White House activities intended to highlight Obama’s infrastructure initiative, unveiled a month ago as the White House came under increasing pressure to address unemployment before the Nov. 2 congressional elections. The proposal would create an infrastructure bank to prioritize projects of national importance and fund it with $50 billion generated by eliminating certain tax benefits for oil and gas companies.

Also Monday, the Treasury Department and Council of Economic Advisers released a report concluding that this is the “optimal time” to invest in public works projects, not only because of the high jobless rate but also because of low prices in the construction sector. And Obama met with a bipartisan group of mayors, governors and transportation officials, all eager to see money flow to neglected projects.

The group included Govs. Edward G. Rendell, D-Pa., and Jack Markell, D-Del., along with the mayors of Los Angeles, Baltimore, Oklahoma City, San Antonio, Columbus, Philadelphia, Atlanta and Charleston, S.C. Also present: former transportation secretaries Sam Skinner and Norman Mineta, who last week released a separate report saying that the nation needs to spend $134 billion to $194 billion just on basic repairs.

With concern rising about the nation’s growing debt, that figure is more than the federal government can provide, administration officials said. Instead, they are pressing for the $50 billion infrastructure bank as the first portion of a six-year plan for transportation funding that has been under discussion for months in Congress.

With elections fast approaching, however, Obama’s exhortations fell on a deserted Capitol. The vast majority of lawmakers are back home campaigning to keep their jobs. Democrats are battling to maintain control in both the House and Senate, despite polls showing a wave of support for the GOP. Republicans need to pick up 39 seats in the House and 10 in the Senate to wrest control of Congress from the Democrats.

Administration officials said action on the infrastructure plan is unlikely until next year.

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