WASHINGTON — President Obama. eager to promote his administration’s efforts to revive the job market on the eve of another politically significant employment report, signed a bill on Thursday that will roll back restrictions on the way start-up companies can raise money from individual investors.

Mr. Obama, surrounded by a bipartisan tableau of lawmakers and entrepreneurs, said the bill known as the JOBS Act, for Jump-Start Our Business Start-Ups, was a “potential game changer” for fledgling businesses in need of financing. Among other things, it would allow them to raise small sums from investors via the Internet.

“For the first time, ordinary Americans will be able to go online and invest in entrepreneurs that they believe in,” Mr. Obama said in a ceremony in the Rose Garden, as Republican supporters of the law, including Representative Eric Cantor of Virginia, the House majority leader, looked on.

New businesses generate almost every new job in the United States, Mr. Obama said, hence the bill’s acronym. On Friday, the White House will highlight another facet of its jobs campaign with a daylong forum on women and the economy.

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President Obama signed a bill on Thursday to ease restrictions on the way start-up companies can raise money from investors. Credit Stephen Crowley/The New York Times

The bill-signing set the stage for Friday’s release of the monthly employment report by the Labor Department, which has become an important political barometer for the presidential election. There have been signs of strengthening in the last several employment reports.

“Our economy has begun to turn a corner,” the president said, “but we’ve still got a long way to go. We’ve still got a lot of Americans out there who are looking for a job or looking for a job that pays better than the one that they’ve got.”

Responding to critics who say the law will open the door to investor fraud, the president insisted that these Web sites would be closely monitored by the Securities and Exchange Commission. He also appealed for adequate funding for the S.E.C. shooting a glance at Mr. Cantor and his fellow Republicans.

But the White House was mainly celebrating a rare bipartisan achievement on legislation that had been by pushed by Republicans and embraced by Mr. Obama in his State of the Union address. Most of the administration’s $447 billion jobs bill has little chance of being passed by a hostile Congress in an election year.

Mr. Cantor joined in the unusual display of harmony, saying to reporters at the White House after the ceremony: “I hope it represents the kind of bipartisan work that we can accomplish here in Washington over the next few months. We have a very difficult economic situation still.”

While Mr. Cantor said he welcomed the improvement in the job market, he added, “We are nowhere near out of the woods.” With the summer travel season approaching, he said, high gas prices were putting a burden on families.

The speaker of the House, John A. Boehner of Ohio, also welcomed the bill, which he described in a statement as a “key part of the Republican jobs plan.” Mr. Boehner said it would be “good news for entrepreneurs and aspiring small businesspeople struggling to overcome government barriers to job creation.”

Also onstage with Mr. Obama was Steve Case, an investor and co-founder of America Online, who is a member of the President’s Council on Jobs and Competitiveness. Mr. Case praised the law but urged the White House to push for other measures, including legislation to allow highly skilled immigrants to stay in the United States.

The audience included venture capitalists and entrepreneurs who had lobbied for the easing of regulations. Several said the law would open the door to so-called crowd-funding, in which a start-up can solicit small investments from individuals through Web sites registered with the S.E.C.

Critics of the law, including the former New York attorney general, Eliot Spitzer. say it will weaken a 2003 legal settlement, negotiated by Mr. Spitzer, that protects investors by forbidding Wall Street research analysts to promote stocks to help bankers at the same firm win deals.

But the White House press secretary, Jay Carney, said the law would keep in place “the core post-dotcom bust conflict-of-interest protections from the Spitzer decree.” Investment banks, he said, must still keep their research and banking departments separate; research analysts cannot do sales presentations for stock offerings.

While soliciting investment funds online has triggered fears of fraudulent schemes, the law’s backers said the greater availability of information through social media sites like Facebook would allow would-be investors to conduct their own background checks, making it difficult for such schemes to succeed.

“While it seems reasonable to worry about these issues, there is just so much more information these days,” said Timothy Rowe, the chief executive of the Cambridge Innovation Center, which provides office space for start-up firms next to the campus of the Massachusetts Institute of Technology.

A version of this article appears in print on April 6, 2012, on page A12 of the New York edition with the headline: Obama Signs Bill to Promote Start-Up Investments. Order Reprints | Today’s Paper | Subscribe