A week after President Obama announced an executive action to reform the nation’s immigration system, city officials are struggling to determine how many people in Portland could potentially qualify for temporary protection from deportation.

Obama’s executive action would allow nearly 5 million illegal immigrants to temporarily stay in the United States without fear of deportation and refocus immigration enforcement on “felons, not families.” The announcement drew a strong rebuke from Republicans, who criticized the president for taking action without the consent of Congress.

Mayor Michael Brennan, who said the reforms would have a “substantial impact” in the city, has been invited to participate in an immigration summit in New York along with representatives of at least 20 progressive U.S. cities to implement immigration reforms.

“Obviously, this is a major issue in the city of Portland,” Brennan said Friday.

But it’s unclear how many immigrants in Portland would actually be affected by Obama’s immigration reforms, which largely focus on people who have been in the United States illegally for at least five years and have children who are U.S. citizens. These immigrants would be shielded from deportation for three years and given work permits, provided they pass background checks and pay fees.

Brennan noted that the city only considers financial need, not immigration status, when people apply for General Assistance.

Both the Pew Research Center and the nonpartisan, nonprofit Migration Policy Institute estimate there are fewer than 5,000 illegal immigrants in Maine. The MPI conducted an analysis of how many immigrants in more than 40 states would be covered by the president’s reforms, but that analysis did not include Maine because the number was too small.

City Hall spokeswoman Jessica Grondin said the city estimates that roughly 15 percent of Portland’s 10,000 immigrants could be affected, but immigration advocates said that estimate seems high.

Those 1,500 immigrants largely comprise the city’s Hispanic population, according to Regina Phillips, the director of the city’s Refugee Resettlement Office. Phillips described it as a “very rough” estimate.

That estimate, however, assumes that Hispanics are mostly here illegally and would qualify for the reforms outlined by the president, which is not likely, according to Sue Roche, executive director of the Immigrant Legal Advocacy Project, a Portland-based nonprofit that helps immigrants apply for asylum.

“A lot of people have been asking. Unfortunately, we just don’t know,” Roche said.

Although the reforms apply to qualified immigrants from all countries, most of the city’s immigrants have been resettled through official refugee resettlement programs, such as Catholic Charities, or have come to the United States on valid visas and then applied for asylum, and therefore would not qualify.

Those mostly likely to be affected are Hispanics who have been here at least five years and have a child that was born in the United States or is now a legal permanent resident, Grondin said.

There are 218 students enrolled in the Portland public school system whose primary language is Spanish, according to Grace Valenzuela, the director of the district’s Multilingual & Multicultural Center. It was not immediately known how many were born in the United States, Valenzuela said, but the district does not know the legal status of their parents.

“We don’t ask those kinds of questions,” she said.

Valenzuela also noted that only one student has applied to qualify for protection from deportation under the Deferred Action for Childhood Arrivals program. Enacted by Obama in 2012, DACA allows some children who came to the United States illegally to stay and work here temporarily without fear of deportation.

Anecdotally, however, “a lot” of immigrants in Portland could be affected by Obama’s reforms, according to Rene Pena Jr., whose family owns La Bodega Latina on Congress Street, a grocery store and meeting place for the city’s Hispanic population.

Pena said Hispanics were eager to hear the details of Obama’s reforms last Thursday. Many people stocked up on food and beer and stayed home to watch the president’s address, he said.

Since then, however, the excitement has faded, with some expressing skepticism that the immigration system would be reformed.

“Sometimes when something has happened and people are happy, you see them more,” Pena said. “But (Obama) spoke, and the next day it was like nothing happened.”

Nevertheless, Portland is one of at least 20 of the nation’s most progressive cities – including San Francisco and Seattle – being invited to the Dec. 8 summit at Gracie Mansion, according to New York City Mayor Bill de Blasio.

Although The New York Daily News reported Brennan would attend, Portland’s mayor said Tuesday he is still assessing whether he will attend in person.

Brennan noted that there are between 1,500 and 2,000 asylum seekers in Portland. He hopes that the immigration reforms outlined last week will open the door to additional reforms that could streamline the asylum process, which can take years, and free up more funding.

De Blasio said the summit will focus on ways cities across the country implement Obama’s immigration plan. Mayors will be charged with developing a five-point plan for implementing the reforms, he said.

Portland’s invitation reaffirms its reputation as one of the most progressive cities in New England. The city led the way in making it illegal to discriminate against someone based on their sexual orientation before the Legislature did, and it recently voted to legalize recreational use of marijuana – although state law supersedes that action.

Throughout his term, Brennan has reaffirmed that Portland is an open and welcoming place for everyone, including immigrants. He has also been at the forefront of defying Gov. Paul LePage’s effort to cut off assistance to undocumented immigrants, including people who came to the United States legally seeking asylum.

“We can’t wait any longer for immigration reform,” Brennan said in a written statement posted on de Blasio’s website. “I’m pleased President Obama is taking action as this reform will have a substantial impact on the people of Portland and Maine as a whole.”