Today is the first day that as many as 1.7 million young undocumented immigrants who were brought to the United States as children can file applications for deferred action, under a new policy announced by President Obama in June. Instructions for the applications were posted on the U.S. Citizenship and Immigration Services (USCIS) website Tuesday afternoon. If approved, these immigrants would be allowed to live and work openly in the United States for a two-year period that could then be extended.

USCIS, which normally reviews about 6 million applications for citizenship, residency and work visas every year, will review the applications for deferred action. It is not known how many people will apply or when. The greatest numbers of beneficiaries will be in the states of California, Texas, Florida, New York, and Illinois.

Both advocates and critics warn of potential budget shortfalls and back-ups in processing paperwork. Alejandro Mayorkas, director of USCIS, said that “while individual processing times may vary, individual requests will take several months to process.” No new USCIS workers have been hired to review the school records, affidavits and other documents that applicants will be required to file, and no additional funds have been allocated to cover the additional processing costs. USCIS expects costs to be covered by the application fees.

Under the program, called “Deferred Action for Childhood Arrivals,” undocumented immigrants under the age of 31 who arrived in the U.S. before turning 16 years old would be eligible for deferred action and a renewable two-year work permit if they are currently enrolled in school, graduated from high school or served in the U.S. armed forces, and have no criminal record, among other criteria. The program does not confer any permanent legal status or open a future path to citizenship. While the policy offers immigration advocates and undocumented immigrants cause for optimism, several states continue to move forward with new immigration policies that may dampen some of the euphoria around the new policy.

Advocacy groups around the country have planned celebrations, legal aid seminars and other events to mark the occasion and provide support to applicants. The office of the New York Immigration Coalition (NYIC), a leading advocate for immigrant communities that has worked with AS/COA, was flooded over the weekend with young immigrants seeking information about the applications, as were many similar organizations in other cities. Jacqueline Esposito, director of immigration advocacy at NYIC, said, “We recognize that this particular relief is limited in nature, but we believe it’s going to build momentum to more lasting reform.”