The United States used to lead the world in the number of 25- to 34-year-olds with college degrees. Now it ranks 12th among 36 developed nations.

“The growing education deficit is no less a threat to our nation’s long-term well-being than the current fiscal crisis,” Gaston Caperton, the president of the College Board, warned at a meeting on Capitol Hill of education leaders and policy makers, where he released a report detailing the problem and recommending how to fix it. “To improve our college completion rates, we must think ‘P-16’ and improve education from preschool through higher education.”

While access to college has been the major concern in recent decades, over the last year, college completion, too, has become a leading item on the national agenda. Last July, President Obama announced the American Graduation Initiative, calling for five million more college graduates by 2020, to help the United States again lead the world in educational attainment.

This month, on becoming chairman of the National Governors Association, Gov. Joe Manchin III of West Virginia announced that he would lead a college-completion initiative.

In May, Grantmakers for Education, an organization for those who make gifts to educational programs, convened a group of philanthropists and policy experts to talk about how to bolster college-completion rates.

“We spend a fortune recruiting freshmen but forget to recruit sophomores,” Michael McPherson, president of the Spencer Foundation, said at the meeting.

In April, Melinda Gates gave a speech at the American Association of Community Colleges convention, urging community college officials to lead the way on college completion and pledging that the Bill and Melinda Gates Foundation would contribute up to $110 million to improve remedial programs, in an effort to increase graduation rates.

“The stars are aligning in a way that gives me some hope,” said William Kirwan, chancellor of the University System of Maryland, who hosted the Washington discussion along with Mr. Caperton. “This is a problem that’s been around for too long. But now there’s beginning to emerge a focus of attention and activity that quite frankly we haven’t had till now.”

Mr. Kirwan said that the United States had fallen behind other countries over several decades.

“We led the world in the 1980s, but we didn’t build from there,” he said. “If you look at people 60 and over, about 39-40 percent have college degrees, and if you look at young people, too, about 39-40 percent have college degrees. Meanwhile, other countries have passed us by.”

Canada now leads the world in educational attainment, with about 56 percent of its young adults having earned at least associate’s degrees in 2007, compared with only 40 percent of those in the United States. (The United States’ rate has since risen slightly.)

While almost 70 percent of high school graduates in the United States enroll in college within two years of graduating, only about 57 percent of students who enroll in a bachelor’s degree program graduate within six years, and fewer than 25 percent of students who begin at a community college graduate with an associate’s degree within three years.

The problem is even worse for low-income students and minorities: only 30 percent of African-Americans ages 25-34, and less than 20 percent of Latinos in that age group, have an associate’s degree or higher. And students from the highest income families are almost eight times as likely as those from the lowest income families to earn a bachelor’s degree by age 24.

The problem begins long before college, according to the report released Thursday.

“You can’t address college completion if you don’t do something about K-12 education,” Mr. Kirwan said.

The group’s first five recommendations all concern K-12 education, calling for more state-financed preschool programs, better high school and middle school college counseling, dropout prevention programs, an alignment with international curricular standards and improved teacher quality. College costs were also implicated, with recommendations for more need-based financial aid, and further efforts to keep college affordable.