ALEXANDRIA, Va. — The office manager pressed forward, glowering, his muscles straining the seams of his pinstriped suit. "I'm asking you to step outside," he said.

The nine men and women who had taken over the lobby of AlliedBarton Security Services did not budge.

Rabbinical student clasped hands with Islamic scholar and Methodist seminarian. Heads bowed, they sang "Amazing Grace" — and prayed that the security guards employed here would join the Service Employees International Union.

Struggling to regain power and prestige for the sagging labor movement, the AFL-CIO has hired more than three dozen aspiring ministers, imams, priests and rabbis to spread the gospel of union organizing across the nation this summer.

The program seeks to recreate the historic partnership between faith and labor, an alliance that for nearly a century gave union leaders an aura of moral authority.

As it prepares for a national convention next week in Chicago, the AFL-CIO faces stark challenges: Less than 8 percent of private-sector workers belong to unions, compared with more than 35 percent in the 1950s. Calling the federation so weak that it risks irrelevancy, several member unions have threatened to secede.

Labor leaders are responding with programs to overhaul their image. They want unions to be seen as a dynamic force for social justice, not as a stodgy special interest.

That's where the seminary students come in.

For a stipend of $300 a week, they are organizing security guards in Washington, carpenters in Boston, hotel maids in Chicago, meat packers in Los Angeles. Some spend their days with the workers, trying to give them courage to mobilize. Others visit local congregations to urge solidarity with the union cause.

The interns also march on management, quoting Scripture, hoping the power of prayer — and a bit of embarrassing public theater — might force contract concessions.

"We're showing up in their office, telling them that God does not want them to act the way they're acting toward their workers," said rabbinical student Margie Klein, 26.

Most of the interns can readily quote the religious text that moved them to apply for the labor internship, which is co-sponsored by Interfaith Worker Justice, a nonprofit advocacy group.

John Flack, who will be ordained in the Evangelical Lutheran Church, talks about the biblical injunction to "love thy neighbor."

Ali Abrams, a rabbinical student in Los Angeles, expresses concern that "though these people are made in the image of God, they're not being treated that way."

Born-again Christian Jerad Morey finds motivation in the stories workers have told him about forced overtime, on-the-job injuries and schedules forever in flux. They're pushed so hard, he said, they don't have the chance to "lead an abundant life" — to read, to play with their children, to worship. "They're not living up to their divine potential," he said.

For all their idealism, several interns said they took the job not at all certain that unions were a force for good. As Flack put it, he worried he would find "a lot of corruption and complacency."

So far, he said, he hasn't. The tough part has been persuading other ministers to set aside their stereotypes, he said.

The AFL-CIO's long-term goal is to inspire a generation of pastors to put economic justice — and, in particular, union building — at the center of their ministry.

"There's always been a bond, but this is the first time we've really focused on building a coalition with the faith community," said Nancy Lenk, who directs union internships for the AFL-CIO.