The Senate last night overwhelmingly voted in favor of U.S. acquisition of two destroyers that the Navy never asked for until recently. The 62-to-26 vote could add $700 million to the federal deficit this year.

The issue under consideration was whether the United States should pay Litton Industries the $700 million to acquire the two ships, originally ordered by the Shah of Iran. The new Iranian government has canceled the order, leaving Litton's Ingalls Ship-building Division with four partially completed destroyers that do not meet U.S. Navy specifications.

In the Budget Committee several weeks ago, Sen. Donald W. Riegle Jr. (D-Mich.) moved to eliminate from the Senate budget resolution $1.35 billion for the United States to acquire the ships. The motion carried, but due to a mistake or a mixup, the budget resolution reached the floor with money for two destroyers still included.

Riegle pleaded with his colleagues yesterday to eliminate that money. Approval of the $700 million would be "the most powerful symbolic message that comes out of the 1980 budget process," Riegle said, warning that the public would be outraged when it realized how the United States was bailing out Litton.

But Riegle was up against one of the last of the Senate's powerful southern committee chairmen, John C. Stennis (D-Miss.). Stennis chairs the Armed Services Committee, which has voted to acquire the four Spruance-class destroyers, which are being built by about 2,000 of Stennis' constituents at the Ingalls shipyard in Pascagoula, Miss.

Until the fall of the shah, the U.S. Navy had never asked for these or comparable destroyers, and they are not mentioned in its current five-year shipbuilding program.

But since the Iranian revolution, the Pentagon has decided it wants the ships.In debate on the Senate floor last night, Stennis said the issue was whether the Navy should be deprived of warships it needs and wants. He denied any personal interest just because the ships are being built in Mississippi.

Stennis also said it would cost the United State $800 million more to acquire four comparable ships if it passes up the "bargain" offer of $1.3 billion to buy those Iran had ordered.

Riegle countered that the ships ordered by Iran are not equipped to U.S. Navy standards because they do not carry the most advanced Navy antiaircraft weaponry needed to make them effective against the latest Soviet aircraft.

The Senate will get another chance to vote on the issue next week, when it is expected to consider the ship-buying plan separately in a defense authorization bill.

The Senate worked until after midnight on the budget resolution, passing it on a 64 to 20 vote. The $432.6 billion budget for fiscal year 1980, only $200 million above that recommended by the Budget Committee, is $6.5 billion below President Carter's proposal. The Senate indicated it will delay further tax cuts until 1982 rather than make wholesale reductions in federal spending.

The House is scheduled next week to consider the spending plan recommended by its Budget Committee.