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Millions of illegal immigrants would be put on a pathway to legal status and eventually have the chance to apply for citizenship in exchange for paying fines and taxes, under the terms of the immigration overhaul being unveiled this week.

According to an outline of the bill released to Fox News late Monday night, the massive legalization program would be twinned with a multibillion-dollar effort to boost border security.

It would require the Homeland Security Department to create and launch plans for border security and fencing before illegal immigrants can enter a provisional status. This could happen as early as six months after enactment of the bill.

They would remain in that provisional status for 10 years, able to work legally but barred from federal benefits like welfare or health care. After 10 years they could seek green cards conferring permanent legal status, provided the security and fencing plans have been "substantially" carried out. After another three years, those immigrants could petition for citizenship.

In total, the bill creates a minimum 13-year path to citizenship for up to 11 million illegal immigrants, costing them each $2,000 in fines plus additional fees. Applicants would have to meet other criteria as well in order to qualify.

It's unclear whether the border security "triggers" will be enough to satisfy skeptical lawmakers. The bill outline establishes numeric goals for border apprehensions, but it's unclear how closely meeting -- or missing -- those goals is tied to the pathway to legal status.

Conservatives say border security improvements should be verified before illegal immigrants can seek citizenship. Illegal immigrant advocates say their pathway should not be held up by that process.

Regardless, the plan dedicates billions to security efforts, including $3 billion to providing more border agents, customs agents and surveillance systems along the border; and $1.5 billion to building up border fencing.

The security and legalization efforts, though, are only part of the sweeping plan.

The legislation also would remake the nation's inefficient legal immigration system, creating new immigration opportunities for tens of thousands of high- and low-skilled workers, as well as a new "merit visa" aimed at bringing people with talents to the U.S. Senators had planned to formally introduce the bill Tuesday, but after Monday's bombing at the Boston Marathon a planned press event was delayed until later in the week.

Employers would face tough new requirements to check the legal status of all workers.

Overall, the changes represent the most dramatic overhaul to U.S. immigration law in more than a quarter-century.

"There's a realization among most Republicans and Democrats that this issue needs to be addressed," said Sen. John McCain, R-Ariz., a leader of the effort. "You can't have 11 million people living in the shadows forever."

McCain and another leader of the group, Sen. Chuck Schumer, D-N.Y., were to meet with President Obama on Tuesday to brief him on the legislation. It's a top second-term priority for the president.

The bill is the result of months of secretive negotiations among eight lawmakers. In addition to Schumer and McCain, they are Democrats Dick Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado, working with Republicans Marco Rubio of Florida, Lindsey Graham of South Carolina and Jeff Flake of Arizona.

The legislation is a painstaking attempt to balance a focus on border security and legal enforcement sought by Republicans in the group with Democratic priorities like making citizenship widely accessible. Crafting the bill was a time-consuming process of seeking compromise and bringing together traditionally opposed groups, such as the U.S. Chamber of Commerce and the AFL-CIO, the United Farm Workers and the American Farm Bureau Federation.

But even harder work lies ahead now that legislative language will become public for other lawmakers and groups on all sides to examine and react to. The Senate Judiciary Committee will hold hearings on the bill beginning Friday and likely move to amend and vote on it in May, with action on the Senate floor expected later in the summer. The Republican-controlled House also must act, and opposition from some conservatives there is likely to be fierce.

"The Senate proposal issues an open invitation to enter the country illegally," Rep. Lamar Smith, R-Texas, said on the House floor Monday. "Millions more will do so before the border is secure. The Senate proposal will dramatically increase illegal immigration."

People brought here illegally as youths would have a faster path: They could get green cards in five years and would become eligible for citizenship immediately thereafter.

U.S. citizens no longer would be able to sponsor their siblings for eventual U.S. citizenship, a change activist groups have opposed. That's among several changes aimed at rebalancing an immigration system that now awards around 15 percent of green cards to people with employment ties, and the majority to people with family ties, to a system that awards 45 percent to 50 percent of green cards based on employment ties.

There would be no limit in the number of green cards awarded to people of extraordinary ability in science, arts, education, business or athletics, or to outstanding professors, doctors and others. A new startup visa would be created for foreign entrepreneurs trying to come here to start their own companies.

Visas for highly skilled workers greatly in demand by technology companies would nearly double. Low-skilled workers would be able to come in for jobs in construction, long-term care and other industries, ultimately up to 200,000 a year. A new agriculture visa program would bring farm workers to the U.S.; farm workers already here illegally would get a faster path to citizenship than others here illegally, able to seek a green card in five years, an effort to create a stable agricultural workforce.

The bill is titled the "Border Security, Economic Opportunity and Immigration Modernization Act of 2013."

The Associated Press contributed to this report.