Robert Galbraith / REUTERS

America has always been a nation of immigrants, but today, there is general agreement that the U.S. immigration system is broken. The southern border remains porous, there are 11 million undocumented immigrants living in the shadows, and tens of thousands of the most promising immigrants are forced to leave the country thanks to outdated visa rules. Now, some of the wealthiest and most successful tech executives and investors in the country — led by Facebook founder Mark Zuckerberg — are calling for immigration reform.

“We have a strange immigration policy for a nation of immigrants,” Zuckerberg wrote Thursday in the Washington Post. “And it’s a policy unfit for today’s world.” Zuckerberg has joined forces with top executives and founders from Google, Yahoo and LinkedIn to launch a new organization called FWD.us, with the goal of influencing the current debate. Several top venture capitalists are also participating. “To lead the world in this new economy, we need the most talented and hardest-working people,” Zuckerberg wrote. “We need to train and attract the best.”

(MORE: Vivek Wadhwa: Stop the U.S. Highly-Skilled ‘Immigrant Exodus’ Now)

Visa reform is particularly important for these tech titans because immigrants have played such an important role in Silicon Valley. “Immigrants are far more likely than natives to study science and engineering and more likely to produce innovations in the form of patents,” University of California economist Gordon Hanson wrote in a 2011 study. “Expanding the supply of immigration visas for high-skilled workers increases patenting activity in science and engineering, particularly in U.S. high-tech firms.”

But thanks to outdated visa rules, tens of thousands of skilled immigrants are forced to return home — after being educated in the U.S. — because the government does not issue enough H-1B visas. This has led to what author Vivek Wadhwa has called America’s “immigrant exodus.” This “reverse brain drain” of talent is having real consequences. The proportion of immigrant-founded companies nationwide has slipped from 25.3% to 24.3% since 2005, and in Silicon Valley, the percentage of immigrant-founded start-ups declined from 52.4% to 43.9% during that time, according to a recent study co-authored by Wadhwa and the Kaufman Foundation.

Many tech executives — starting with the late Steve Jobs — have argued that there aren’t enough American-born math and science graduates to fill the engineering jobs in Silicon Valley’s booming economy, and thus we need to attract, and keep, the best and brightest foreign-born workers. A recent study by the consulting firm McKinsey found that 45% of U.S. employers surveyed say that a “skills shortage” is a leading reason for entry-level vacancies. In a widely discussed 2011 Wall Street Journal article, Marc Andreessen, arguably Silicon Valley’s top venture capitalist, wrote that “every company I work with is absolutely starved for talent.”

(MORE: The Economics of Immigration: Who Wins, Who Loses and Why)

Others have called such claims exaggerated, and suggested these jobs could go to American-born tech workers. These critics say the H-1B program allows U.S. companies to train foreign workers and then “outsource” them abroad at lower wages, thus hurting U.S. workers. And some tech experts say that the immigration debate “has to start with the education and re-education of the American workforce.”

In any event, this has become a major issue for Silicon Valley. “Why do we kick out the more than 40% of math and science graduate students who are not U.S. citizens after educating them?” Zuckerberg asked. “Why do we offer so few H-1B visas for talented specialists that the supply runs out within days of becoming available each year, even though we know each of these jobs will create two or three more American jobs in return? Why don’t we let entrepreneurs move here when they have what it takes to start companies that will create even more jobs?”

The answer, according to Wadhwa, is that the toxic state of U.S. politics and the rancorous debate over illegal immigration have made immigration reform all but impossible in recent years. “Both the Democrats and the Republicans agree that we want the entrepreneurs, the scientists, the doctors, the researchers,” Wadhwa told me last fall. “Everyone agrees that we want these people to stay. But there’s a stalemate on the issue of amnesty for illegal workers.”

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There are signs in Washington, D.C., that a grand bargain on immigration reform may be on the horizon, and Zuckerberg and his allies clearly want to influence its contours. FWD.us is calling for comprehensive immigration reform that “begins with effective border security, allows a path to citizenship and lets us attract the most talented and hardest-working people, no matter where they were born.” The group is also calling for higher standards in schools, a “much greater focus” on science, technology, engineering and math, and more investment in scientific research.

For Zuckerberg, as for so many Americans, immigration is also a personal issue. “My great-grandparents came through Ellis Island,” he wrote. “My grandfathers were a mailman and a police officer. My parents are doctors. I started a company. None of this could have happened without a welcoming immigration policy, a great education system and the world’s leading scientific community that created the Internet.”