Senate Majority Leader Robert Byrd (D-W.Va.) yesterday attacked a constitutional amendment requiring a balanced federal budget, charging it would endanger national defense and shackle the government's ability to deal with the economy.

A balanced budget amendment "sounds good," Byrd told a news confercnce, but quickly added, "Let's not straitjacket Congress by wrapping it in the chains of a balanced budget."

His remarks were the most strongly worded comments from a major figure in the Democratic Party since California Edmund G. (Jerry) Brown Jr. called for a balanced-budget amendment almost two weeks ago.

When President Carter was asked about the proposal by Brown, a potential rival for the 1980 presidential nomination, he said he opposed holding a constitutional convention to consider such an amendment because it "would be completely uncontrollable." But as for the amendment itself, the president simply said it "ought to be approached very gingerly, very carefully."

Twenty-two states, acting under a federal constitutional provision that allows states to petition Congress for constitutional amendments, have already passed measures similar to Brown's. Many states' constitutions require them to maintain balanced budgets.

In addition to citing traditional economic arguments, Byrd said a balanced budget amendment would put dangerous pressure on defense spending.

If budget cuts had to be made to comply with the amendment, "This group and that group will be talking about taking it out of national defense," Byrd said.

He also cautioned that state governments which have become increasingly dependent on federal outlays would have "far more difficulties" making ends meet if the amendment were to pass.

On other matters, Byrd said:

He opposes cuts in Social Security benefits included in Carter's new budget. The Carter administration has reportedly proposed eliminating the $255 lump sum death-burial benefit, benefits for surviving children after their 18th birthday and cutting disability benefits.

He is receiving widespread support from both Republicans and Democrats for his proposal to tighten rules on Senate filibusters.

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