Travelers arriving in the United States are likely to face longer lines for a passport stamp as drastic spending cuts known as the sequester begin to bite, the union representing customs and border staff said Thursday.

The National Treasury Employees Union, which represents some 24,000 US Customs and Border Protection staff, said furlough notices were being sent to all personnel, a move likely to snarl up US ports of entry.

Up to 14 unpaid furlough days are likely to go to employees represented by the NTEU, including managers and supervisors.

"There is no escaping the reality that sequestration is having serious effects on the traveling public and on vital commerce," NTEU President Colleen Kelley said in a statement.

"These impacts will only get worse the longer sequestration continues, especially as the busy summer travel season approaches."

Recent reports that processing time had doubled for passengers on flights into Orlando International Airport would become more commonplace because of the spending cuts, an NTEU press release warned.

The Orlando Business Journal reported that passengers arriving on two flights from Britain and Germany this week had to wait two hours to clear customs, instead of the more normal 45 minutes.

On March 1, President Barack Obama implemented the sequester, $85 billion in mandatory cutbacks to government spending over the next seven months, after failing to get Congress to agree on a less severe approach to reducing the federal deficit.