WASHINGTON — Key senators in both parties and the White House announced agreement yesterday on an immigration overhaul that would grant quick legal status to millions of illegal immigrants already in America and fortify the border.

The plan would create a temporary worker program to bring new arrivals to the U.S and a separate program to cover agricultural workers. Skills and education-level would for the first time be weighted over family connections in deciding whether future immigrants should get permanent legal status. New high-tech employment verification measures also would be instituted to ensure that workers are here legally.

The compromise came after weeks of painstaking closed-door negotiations that brought the most liberal Democrats and the most conservative Republicans together with President Bush’s Cabinet officers to produce a highly complex measure that carries heavy political consequences.

Mr. Bush called it “a much-needed solution to the problem of illegal immigration in this country” and said, if approved, the proposal “delivers an immigration system that is secure, productive, orderly, and fair.”

“With this bipartisan agreement, I am confident leaders in Washington can have a serious, civil and conclusive debate so I can sign comprehensive reform into law this year,” he said in a written statement. Mr. Bush planned to make remarks about the bill later yesterday at the White House.

Senator Kennedy of Massachusetts, his party’s lead negotiator on the deal, hailed it as “the best possible chance we will have in years to secure our borders and bring millions of people out of the shadows and into the sunshine of America.”

Anticipating criticism from conservatives, Senator Specter, a Republican of Pennsylvania, said, “It is not amnesty. This will restore the rule of law.”

The accord sets the stage for what promises to be a bruising battle next week in the Senate on one of Mr. Bush’s top nonwar priorities.

The majority leader, Senator Reid, a Democrat of Nevada, called the proposal a “starting point” for that debate, but added that it needs improvement.

“I have serious concerns about some aspects of this proposal, including the structure of the temporary worker program and undue limitations on family immigration,” Mr. Reid said in a statement.

The key breakthrough came when negotiators struck a bargain on a so-called “point system” that prioritizes immigrants’ education and skill level over family connections in deciding how to award green cards.

The immigration issue also divides both parties in the House, which isn’t expected to act unless the Senate passes a bill first.

The proposed agreement would allow illegal immigrants to come forward and obtain a “Z visa” and —after paying fees and a $5,000 fine — ultimately get on track for permanent residency, which could take between eight and 13 years. Heads of household would have to return to their home countries first.

They could come forward right away to claim a probationary card that would let them live and work legally in the U.S., but could not begin the path to permanent residency or citizenship until border security improvements and the high-tech worker identification program were completed.

A new temporary guest-worker program would also have to wait until those so-called “triggers” had been activated.

Those workers would have to return home after work stints of two years, with little opportunity to gain permanent legal status or ever become U.S. citizens. They could renew their guest-worker visas twice, but would be required to leave for a year in between each time.

Democrats had pressed instead for guest workers to be permitted to stay and work indefinitely in America.

In perhaps the most hotly debated change, the proposed plan would shift from an immigration system primarily weighted toward family ties toward one with preferences for people with advanced degrees and sophisticated skills. Republicans have long sought such revisions, which they say are needed to end “chain migration” that harms the economy, while some Democrats and liberal groups say it’s an unfair system that rips families apart.

Family connections alone would no longer be enough to qualify for a green card — except for spouses and minor children of U.S. citizens.

New limits would apply to U.S. citizens seeking to bring foreign-born parents into the country.