The governors of the U.S. Postal Service voted Tuesday to raise rates, including a nickel jump in the cost of mailing a first-class letter, but there could as much as a year of skirmishing before any increase takes effect.

''Even at 30 cents, postage is one of America's best buys," said Postmaster General Anthony M. Frank, noting that U.S. postage remains the lowest in the industrialized world.The proposal calls for the cost of a first-class letter to increase from a quarter to 30 cents, with the price for each additional ounce rising from 20 cents to 23 cents. Post cards would cost 20 cents, also up a nickel, while Express Mail would go from $8.75 to $9.75.

Overall, rates will increase by about 19 percent on all types of mail.

"We cannot ignore that increases in postal operating costs do occur, just as they do in any business," Robert Setrakiam, chairman of the board of governors, said after the vote.

He estimated the increase would cost the average person between $10 and $11 a year.

Mr. Frank said the increases are needed because the post office could face its biggest deficit ever this year, between $1.4 billion and $1.6 billion.

The governors' vote was the first step in a nearly year-long process needed to increase mail rates.

In addition to the first-class increase, the proposal would raise the cost of mailing a typical weekly news magazine from 13.5 cents to 16 cents, while a heavier monthly publication would rise from 29.7 cents to 37.4 cents.

The parcel post rate for a 7-pound package would rise from $4 to $5.06.

Some rate cuts were included for specially prepared business mail that requires little work on the part of the post office.