The US Embassy in Dublin is unable to print visas, passports and other travel documents because of technical problems with the system used to process applications.
It is believed less than 150 people in Ireland, mostly visa applicants, have been affectedby the problem which is impacting on all categories of visa applications.
The embassy has contacted everyone whose visa has been delayed.
The problem will not affect tourists travelling to the US under the visa waiver programme.
Passports will continue to be issued within the six-week standard published on the US department of state website.
The embassy is able to issue passports for emergency travel.
The problems began on Saturday, when a database used for processing visa and passport applications crashed.
Embassies need security approval through this database before it can print passports, visas and reports of births abroad.
It is a US Department of State database, and the outage has affected embassies worldwide.
The database outage resulted in an extensive backlog, which has further hindered the US Embassy’s efforts to return to normal operations.
The cause of the outage is unknown, but according to information contained on the embassy’s website, it occurred soon after maintenance began on the system.
A spokesman for the US Embassy in Dublin said its staff were “working around the clock to fix the problem”.
“The US Embassy Dublin has a very efficient consular services team, and I expect they will clear the backlog quickly once these worldwide technical problems have been resolved,” he said.