Story highlights Mexican President Calderon calls halting deportations of young illegal immigrants "just"

Calderon says Obama showed "valor and courage" in making the "unprecedented" move

The change defers deportation of some who came to the United States illegally as children

The Obama administration rejects Republican claims it is a back-door amnesty

President Barack Obama received praise Monday from Mexico's president for the decision last week to stop deporting some young illegal immigrants.

After the two leaders met one-on-one before the start of the G-20 summit in Los Cabos, President Felipe Calderon thanked Obama for what he called an "unprecedented" move in halting the deportations.

"We believe this is very just," Calderon said, according to an interpreter, adding: "Thank you for the valor and courage that you had in implementing this action. I'm sure many, many families in the United States thank you as well."

Obama made no new comment on the election-year policy change announced Friday that prompted immediate praise from Latino leaders who have criticized Congress and the White House for inaction on immigration reform.

Republicans have reacted with outrage, saying the move amounts to amnesty -- a negative buzz word among conservatives -- and usurps congressional authority.

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In announcing the change in the White House Rose Garden, Obama said it will make immigration policy "more fair, more efficient and more just."

"This is not amnesty. This is not immunity. This is not a path to citizenship. It's not a permanent fix," Obama said to take on conservative criticism of the step. "This is a temporary stopgap measure."

Noting children of illegal immigrants "study in our schools, play in our neighborhoods, befriend our kids, pledge allegiance to our flag," Obama said, "it makes no sense to expel talented young people who are, for all intents and purposes, Americans."

Under the new policy, people younger than 30 who came to the United States before the age of 16, pose no criminal or security threat, and were successful students or served in the military can get a two-year deferral from deportation, Homeland Security Secretary Janet Napolitano said.

It also will allow those meeting the requirements to apply for work permits, Napolitano said, adding that participants must be in the United States now and be able to prove they have been living in the country continuously for at least five years.

The change is part of a department effort to target resources at illegal immigrants who pose a greater threat, such as criminals and those trying to enter the country now, Napolitano said, adding it was "well within the framework of existing laws."

The move addresses a major concern of the Hispanic community and mimics some of the provisions of a Democratic proposal called the DREAM Act that has failed to win enough Republican support to gain congressional approval.

Obama has been criticized by Hispanic-American leaders for an overall increase in deportations of illegal aliens in recent years. Last year, U.S. Immigration and Customs Enforcement removed 396,906 illegal immigrants, the largest number in the agency's history.

Friday's policy change is expected to potentially affect 800,000 people, an administration official told CNN on background. Others put the figure at potentially more than 1 million people.

Hispanics make up the fastest-growing immigrant population in the country, and the Latino vote is considered a crucial bloc for the November presidential election.

Democrats, however, rejected Republican claims that the move was political. Sen. Dick Durbin of Illinois, who sponsored the DREAM Act, noted that Obama repeatedly called for Congress to pass immigration reform legislation, including the DREAM Act. The president acted only after it became clear no progress would come in this Congress, Durbin said.