Sounding notes of hope and challenge, President Obama told the nation Thursday that he is imposing a historic set of executive actions to end congressional gridlock over immigration reform, and balance the rule of law with America's legacy as a welcoming country.

"Mass amnesty would be unfair. Mass deportation would be both impossible and contrary to our character," Obama said in a televised address from the White House.

The critical elements of his plan include cracking down on illegal immigration at the borders; deporting felons and gang members, "not a mother who is working hard to provide for her kids"; and requiring undocumented immigrants eligible for relief to start paying "their fair share of taxes" in exchange for permission to work in the United States without fear of deportation for three years at a time.

"If you meet the criteria, you can come out of the shadows and get right with the law," the president said. "If you're a criminal, you'll be deported. If you plan to enter the U.S. illegally, your chances of getting caught and sent back just went up."

The much-anticipated announcement - hailed as momentous by immigrant aid groups, and derided by critics of illegal immigration as executive overreach - will prevent many deportations while seeking changes that have stalled in Congress over the fate of an estimated 11 million undocumented residents.

As many as five million could qualify under the order, including tens of thousands in Pennsylvania and New Jersey.

"It's a struggle of emotions," said Olivia Vazquez, 20, who was 10 when her parents illegally brought her from Mexico to the United States. She watched Obama's address with a group at a South Philadelphia taqueria. "You feel joy for yourself, but you know that others don't qualify."

The president called his actions "not only lawful" but the kind "taken by every single Republican president and every Democratic president for the past half-century."

Then came the gauntlet.

"To those members of Congress who question my authority to make our immigration system work better," he said, "or question the wisdom of me acting where Congress has failed, I have one answer: Pass a bill."

Obama did not offer details or a timetable for the application process.

But the plan would lift the threat of deportation for immigrants who have lived in the United States for at least five years, passed a criminal-background check, and have a child or spouse who is a U.S. citizen or is a legal permanent resident. Eligible applicants will be allowed to register for work permits, taxpayer ID numbers, and driver's licenses.

Eligibility would also be expanded for Deferred Action for Childhood Arrivals, a two-year-old program under which immigrants who were brought to the United States as children and graduated from high school or served honorably in the military can get renewable protection from deportation and work permits - as Vazquez did. Supporters call these young immigrants "Dreamers."

In some corners, Obama's unilateral move was seen as a strategic political step by a Democratic president facing gridlock from a Republican-dominated Congress in his final two years.

Reaction was swift and partisan.

"The American people want both parties to focus on solving problems together," said Republican House Speaker John Boehner. Obama's " 'my way or the highway' approach makes it harder to build the trust."

Rep. Mike Fitzpatrick (R., Pa.) said: "The president's unlawful orders will drastically increase this problem."

Mayor Nutter, in a statement, called Obama's action "bold and necessary," adding that new Americans in Philadelphia and across the nation "need opportunities that will allow them to succeed."

State Rep. Daryl Metcalfe (R., Butler), the Pennsylvania legislature's most vociferous critic of illegal immigration, said Congress should deny the appropriations necessary to execute Obama's actions.

"Where those dollars would flow," said Metcalfe, "is where Congress needs to shut off the faucet."

But Temple University law professor Jan Ting, an assistant commissioner of the Immigration and Naturalization Service under President George H.W. Bush, said in an interview that opponents of Obama's actions, including himself, are hard pressed to craft a response.

"We don't really want to shut down the government. We don't want to go the impeachment route. Maybe we'll file a lawsuit and see if we can get the court involved," he said. "But the judiciary has shown reluctance to involve itself in a purely political question."

The announcement spawned TV watching parties and a range of emotions across the region.  

Magali Rodriguez, 24, of Bellmawr, was 3 when she came to Camden from Mexico. She watched the address with her husband and their 6-year-old son. She was especially moved when Obama spoke about a child in Las Vegas who came to this country as a young girl.

Like that child, Rodriguez knew no English when she started school.

"I learned through cartoons, magazines, books," she said. "I learned English just the way Barack Obama said."

Rodriguez is a student at the College of St. Elizabeth in Morristown, N.J., and owns a business. Her dream is to visit Mexico someday; she couldn't go to her grandfather's funeral last year.

She said she was a little let down by Obama's announcement. She had hoped he would discuss creating a pathway to citizenship. But to hear him say that she and others could "come out of the shadows," she said, meant a lot.

The Philadelphia chapter of the American Immigration Lawyers Association just happened to hold its monthly meeting at a Center City restaurant around the time Obama was to speak. Several AILA members welcomed the president's actions.

"If persons are given [legal] status, you are going to see a lot of benefits that reach everybody," said attorney John Vandenberg. "Given working papers, they will pay taxes, and that money can fix roads and bridges. Congress could use it for Head Start - for everybody.

"There are people on the road without insurance, without passing the driver's test. Now they can take the test, get a license, get insurance, and we will all be safer."

Under Obama's plan, the parents of Dreamers are not specifically covered.

"You are offering protection to certain family members and not others, while at the same time saying you want to keep families together," said David Bennion, an immigration lawyer in Philadelphia.

"Nothing is going to be perfect. I know that," he said, but relief for the parents of Dreamers "will be the focus of activism going forward."

Anticipating confusion over who qualifies, and possible exploitation by unscrupulous people who offer to help, the Pennsylvania Immigration and Citizenship Coalition, an advocacy group, is planning a series of informational sessions around the state. "Don't be scammed," read the PICC flier. "Do not pay anyone to apply or hold a place. No application process has been announced yet."

The administrative relief does not specifically protect farmworkers, but this group, too, will suffice for now with half a loaf.

"Something is better than nothing. Getting lawful status, bringing people onto the grid, is going to make it harder for employers to exploit people," said Meredith Rapkin, executive director of Friends of Farmworkers, an advocacy group for farmworkers in Pennsylvania. "And that is great."

mmatza@phillynews.com

215-854-2541

@MichaelMatza1

Inquirer staff writer Allison Steele contributed to this article.