WASHINGTON, Jun. 18 (Reuters) - President Joe Biden on Tuesday announced a new effort to provide a path to citizenship to hundreds of thousands of immigrants in the U.S. illegally who are married to U.S. citizens, an election-year move that contrasts sharply with Republican rival Donald Trump's plan for mass deportations.

At a White House event, Biden criticized Trump for separating migrant families at the U.S.-Mexico border and using incendiary language about immigrants in the U.S. illegally, including comments that they were "poisoning the blood of our country."

"It's hard to believe it's being said, but he's actually saying these things out loud. And it's outrageous," Biden said. "I'm not interested in playing politics with the border or immigration. I'm interested in fixing it."

The new Biden program will be open to an estimated 500,000 spouses who have lived in the U.S. for at least 10 years as of June 17, officials said on Tuesday. Some 50,000 children under age 21 with a U.S.-citizen parent also will be eligible.

Biden, a Democrat seeking a second term in the Nov. 5 presidential election, took office vowing to reverse many of Trump's restrictive immigration policies. But faced with record levels of migrant arrests at the U.S.-Mexico border, Biden has toughened his approach.

Earlier this month, Biden barred most migrants crossing the U.S.-Mexico border from requesting asylum, a policy that mirrored a similar Trump-era asylum ban and drew criticism from immigration advocates and some Democrats.

Biden's planned legalization program for spouses of U.S. citizens could reinforce his campaign message that he supports a more humane immigration system and show how he differs from Trump, who has long had a hardline stance on both legal and illegal immigration.

"The Statue of Liberty is not some relic of American history," Biden said. "It still stands for who we are."

The program will almost certainly face legal challenges and a future president could attempt to end it. Texas Governor Greg Abbott, a Republican whose state has battled Biden in court over immigration policy, said in a statement that the new effort was "blatantly illegal" and "pandering for votes."

The U.S. already provides a path to citizenship for immigrants who are married to Americans and entered the country legally on a visa. But in most cases, those who enter illegally must first leave the U.S. for years before being allowed to return legally.

The new program will allow the spouses and their children to apply for permanent residence without traveling abroad, removing a potentially lengthy process and family separation. The administration aims to launch the program in coming months and it remains unclear how long it would take for spouses to obtain permanent residence.

If they are granted permanent residence, they could eventually apply for U.S. citizenship. People who are considered public security threats or who have disqualifying criminal history would not be eligible.

The implementation will roll out in coming months and the majority of likely beneficiaries would be Mexicans, Biden officials said on a call with reporters.

Mexico's President Andres Manuel Lopez Obrador on Tuesday said the decision to regularize Mexican families' migratory status in the United States is "very good news", celebrating Biden's announcement during a press conference.

Biden's White House remarks were tied to the anniversary of the Deferred Action for Childhood Arrivals program.

Former President Barack Obama and then-Vice President Biden launched the DACA program in 2012, another major legalization effort that currently grants deportation relief and work permits to 528,000 people brought to the U.S. as children.

The Biden administration also announced guidance to make it easier for DACA recipients to obtain skilled-work visas.

DACA enrollee Javier Quiroz Castro joined Biden at the White House and said the program allowed him to work legally as a nurse in Houston, including during the COVID-19 pandemic.

"It allowed me to live and work and build a family in the only country I have ever known and loved," he said.

Photo from Reuters