Virginia Gov. John N. Dalton urged the Nuclear Regulatory Commission yesterday to reverse a new policy that is expected to delay start up of Virginia Electric and Power Co.'s North Anna II nuclear plant.

The governor said a delay could cost the utility's customers $12 million to $13 million a month in higher electric bills.

In a letter to NRC Chairman Joseph M. Hendrie, Dalton said that the agency's plan to defer licensing of new plants, including North Anna II, would impose "an unacceptable economic harship" on Virginia.

The Nuclear Regulatory Commission has decided not to grant any operating or construction licenses for nuclear power plants until it adopts new safety, siting and emergency standards. The move is expected to delay the licensing of at least four plants, including North Anna II.

"North Anna II has been ready for licensing since late June, and it is expected that all modifications required by the NRC, including those that resulted from the Three Mile Island analysis, will be completed in January 1980," Dalton said. The North Anna plant is located in Louis County on the North Anna River about 70 miles south of Washington.

Vepco officials say a delay in operating North Anna II will increase cost to consumers because the utility will have to rely on other, more expensive fuels to generate electricity.