Passengers travelling to the United States from Ireland and elsewhere would face stricter Covid testing requirements under plans under consideration by the Biden administration.
Under the proposals which are reportedly being examined, those travelling to the United States, including returning Americans, would have to be tested one day prior to boarding their flights, rather than within three days as is the case at present.
US media reported on Tuesday that officials were also looking at plans that would involve travellers to the United States having to undergo re-testing for Covid-19 within three to five days after arrival.
In addition, the Washington Post reported on Tuesday night that the Biden administration was understood to be considering controversial proposals which would see all travellers, including American citizens, having to self-quarantine for seven days even if they have negative test results.
Media reports said a new system of fines and penalties could be introduced for the first time for those who breached the new requirements.
The two new testing measures are understood to be set out in draft public health proposals drawn up by the Centers for Disease Control and Prevention in the United States and which are currently being assessed by administration officials in Washington.
The proposal for self-quarantine is not understood to be in the draft but some officials have suggested to US media that it could be added later.
Any new tightened restrictions, if introduced, would affect thousands of people planning to travel from Ireland in the weeks ahead.
The moves would form part of a new drive by the Biden administration to tackle the threat posed by the new Omicron variant.
President Joe Biden has already introduced travel restrictions on flights from southern Africa and strongly urged Americans to take vaccinations or a booster shot.
On Tuesday Rochelle Walensky, director of the Centers for Disease Control and Prevention, said the agency was looking at tighter measures for travellers such as narrowing the testing window and adding quarantine requirements in certain cases to help slow the entry of the Omicron Covid variant into the US
President Biden is expected to announce a new strategy for dealing with Covid-19 for the current winter period later this week.