WASHINGTON — Vowing that the "horror" of Oklahoma City must never recur, President Clinton announced new counterterrorism proposals Wednesday that he said would balance concern for civil liberties with the need to ensure "swift, certain and severe" justice for "anyone who dares sow terror on American land."

Summoning congressional leaders to the White House to plan the nation's response to the worst act of terrorism in American history, Clinton urged lawmakers to adopt the proposals swiftly.

The package includes hiring an additional 1,000 FBI agents, prosecutors and other federal law enforcement officials and creating a centralized counterterrorism bureau under the direction of the FBI. "We cannot allow the entire country to be subjected to the horror the people of Oklahoma City have endured," Clinton said. He described the measures as grounded "in common sense and steeled with force."

Leaders from both parties pledged to work with unaccustomed bipartisanship to craft the new law, combining the new proposals with the main features of a pending counterterrorism bill.

But they suggested that they still have reservations about the constitutionality of some of the proposals, particularly those that would expand the FBI's authority to engage in wiretapping and other forms of electronic surveillance.

Senate Majority Leader Bob Dole (R-Kan.) said after the meeting that as tragic as last Wednesday's bombing of the Oklahoma City federal building was, "we need to be very careful in how we proceed. . . . There are certain areas involving people's rights that we have to go very slowly on."

House Speaker Newt Gingrich (R-Ga.) said that any legislation granting federal authorities broader investigative powers must protect "our civil liberties while also protecting us."

Although all of the lawmakers were generally receptive to Clinton's request for more law enforcement personnel, some expressed concern over the cost of hiring as many as 1,000 new agents for the FBI, the Treasury Department's Bureau of Alcohol, Tobacco and Firearms, and other federal agencies.

Participants at the meeting said that White House Chief of Staff Leon E. Panetta estimated the additional costs of the package at $100 million this year, $500 million next year and about $1.2 billion over five years.

"We'll have to look at those issues," said Sen. Don Nickles (R-Okla.). "These are expensive."

Other elements of the combined counterterrorism law include: