WASHINGTON - Congress gave the president power yesterday to cut government spending by scrapping specific programs with a line-item veto, although President Clinton will have to win re-election before he can use it.

Fulfilling a GOP ''Contract With America'' promise, the House followed the Senate in approving the measure, which marks a historic shift in the balance of power between the executive and legislative branches.

Since the nation's founding, the president has been forced to approve or reject legislation in its entirety.

''The Republican Congress has done something that no previous Congress has been able to accomplish since the first line-item veto proposal was introduced in the 1870s,'' said House Government Reform and Oversight Committee Chairman William Clinger, R-Pa., who helped forge the House-Senate compromise plan.

Opponents characterized it as a dangerous ceding to the executive branch of Congress' power of the purse. ''This is fundamentally unwise and it manifests a fundamental disrespect of our own duties,'' Rep. David Skaggs, D-Colo., said.

But constitutional considerations that have blocked passage in the past were overcome by the demand for new tools to combat the federal deficit.

Giving the president authority to delete individual items from spending bills allows him to kill low priority or pork-barrel projects.

''The buck will finally stop at the president's desk,'' said Rep. Jim Bunning, R-Ky. ''We are going to give him the opportunity,'' he said, ''to end the era of pork-barrel spending.''

The bill also allows the president to cancel tax benefits targeted to groups of 100 or fewer beneficiaries and eliminate spending for new entitlement programs that Congress might establish or additions to the food stamp program.

Clinton, like previous presidents a strong supporter of the line-item veto concept, said the bill would ''ensure that our public resources are put to the best possible uses during these times of tight budgets.''

But the president wouldn't be able to use this new power until Jan. 1, a result of an agreement between Clinton and his certain opponent in the presidential elections this fall, Senate Majority Leader Bob Dole, R-Kan. In a telephone conversation last week, the two decided that the law should not go into effect until the new year, so it wouldn't become an issue during the political campaign.

The House defeated, 256-159, an attempt to make it effective immediately.

Dole, too, voiced strong support for the bill: ''Line-item veto seems to be the one thing that all modern presidents agree on,'' he said shortly before the Senate voted 69-31 to pass it Wednesday. ''The president, regardless of party, should be able to eliminate unnecessary pork-barrel projects from large appropriations bills.''

The House approval of the line-item veto Thursday came on a procedural vote, 232-177, connected to a package of measures attached to a bill to raise the federal debt ceiling. That vote, complicated by the fact that some lawmakers opposed the package but supported the line-item veto, separated the line-item veto from the package and allowed it to be sent independently to the president.