The Clinton administration asked the Supreme Court on Monday to uphold Congress' historic decision to let him veto specific items in spending and tax measures.

The 1996 line-item veto law does not violate the separation of powers between Congress and the president, said Solicitor General Seth Waxman."This is not an example of a president repealing a provision of a law that Congress has enacted . . . but exercising a discretionary authority that Congress has given him," Waxman said.

But some justices appeared skeptical.

"From a taxpayer's standpoint, this was a law that's been canceled," said Justice Anthony M. Kennedy.

"That sounds to me like legislating, no matter what legal dressing you want to give to it," added Justice Ruth Bader Ginsburg.

Louis Cohen, a lawyer for an Idaho potato growers' group that challenged the law, said when the president uses the line-item veto, "he is by doing that producing a truncated statute that Congress didn't pass."

The high court is expected to rule by July, but it appeared possible that - like last year - the justices again might not decide whether to uphold the line-item veto.

Waxman argued that the potato growers and New York City, which also challenged the law, lacked legal standing because they were not directly affected by vetoes carried out by Clinton last year. Last year, the justices ruled that six members of Congress who challenged the veto law also lacked standing to sue.

"It's disappointing, you know, we went into a big windup last year without a pitch," said Justice Antonin Scalia, adding that it was "astounding" that this year's case involved two legal challenges brought by groups only indirectly affected by a veto.

Congress voted in 1996 to grant the president line-item veto authority. Clinton exercised the veto 82 times last year before a federal judge here ruled the law unconstitutional in February.

Nearly every president in the past century has sought the line-item veto as a tool for controlling "pork barrel" programs added by lawmakers. Most governors have similar authority over state spending.

The line-item veto law lets the president sign a bill and within five days go back to reject specific spending items or tax breaks in it. Congress could reinstate the item by passing a separate bill.

Waxman conceded that a line-item veto law allowing the president to strike individual items from a bill before signing it would violate the Constitution. But he said the measure approved by Congress allows the president to either spend money allocated by Congress or cancel that spending and allow the money to be used for deficit reduction.

Attorney Charles Cooper, representing New York City, said a line-item veto has the same effect as repealing that part of a law.

In February, U.S. District Judge Thomas F. Hogan ruled the measure an unconstitutional surrender by Congress of an "inherently legislative function" to the president. Once a bill becomes law, the president's sole duty is to carry it out, he said.

Last June, the Supreme Court rejected a challenge to the law by six members of Congress, saying they lacked legal standing to sue. However, the justices said a lawsuit could be filed by anyone affected once the president actually used the veto.