A potential strike by transport unions that would shut down access to commuters trying to reach New York City from neighboring New Jersey would cost the city's businesses $5.9 million per hour, an influential business group said on Monday.

The loss of productivity would be felt most keenly in the city's dominant financial sector, with losses reaching $1.9 million for a one-hour delay, according to the analysis by Partnership for New York City.

"A transit strike is among the most expensive events that can happen to New York City," said Kathryn Wylde, president and chief executive of the organization, which represents many of the city's biggest corporations.

RELATED: NJ Transit reveals contingency plan during possible strike

Transport unions failed to reach agreement with representatives of NJ Transit, which runs rail and bus links into the city, during talks with federal arbitrators in Washington D.C. on Friday.

In the absence of a pact this week, unions have said they will walk off the job on Sunday.

Unions are asking for 2.5 percent annual pay rises in return for increases in employee health-care contributions. They say that is their final offer and they will not accept the 0.6 percent they say NJ Transit is offering.

NJ Transit officials released an emergency plan last week but warned they could only accommodate 38 percent of normal traffic. A strike would displace over 100,000 commuters and lead to snarl-ups on roads and serious overcrowding on alternative public transportation routes, they said.

Officials said a shutdown could force an additional 10,000 cars per hour into rush-hour traffic during peak times, creating tail backs stretching more than 20 miles into New Jersey as drivers jostle to pass through limited crossing points into Manhattan.