WASHINGTON - President Obama urged Republican lawmakers Thursday to approve billions of dollars in new federal spending on roads, bridges and ports as he continued for a second day to try to build momentum for his stalled economic proposals.

Speaking at the port in Jacksonville, Fla., Obama laid out a broad case for spending on infrastructure, arguing that it would ripple through the economy, boost the still-struggling middle class and make U.S. businesses more competitive.

"If we don't make the necessary investments to ensure that America's a magnet for good jobs - investments in education, manufacturing, research, and transportation and information networks - we're just waving the white flag of surrender to other countries as they forge ahead in this global economy," Obama said.

The president offered no new proposals or strategies for passing his familiar plans through a Republican-led House that has rejected such spending for two years.

Obama's remarks were part of a new White House effort to return to economic themes after months of focus on immigration, leak investigations, upheaval in the Middle East and other issues.

As he did Wednesday, when he launched the new push in Illinois and Missouri, Obama said he would outline more detailed plans in the weeks to come and vowed not to wait for Congress.

"The world can't wait for Congress to get its act together," he said.

Obama's visit to Jacksonville was intended to highlight his previous attempt to speed up infrastructure projects without congressional consent.

Last year, as part of his "We can't wait" initiative, Obama ordered federal agencies to expedite a study of the environmental impact of a project to deepen the port to handle supersized cargo tankers. Obama's move cut 14 months off the review process, according to the Florida Ports Council, but the Army Corps of Engineers did not meet the president's April 2013 goal for completing the study.

"Apparently, we can wait," said Rep. Bill Shuster, R-Pa., chairman of the House Transportation and Infrastructure Committee. He said he would introduce legislation to authorize such water projects and streamline the environmental review process.