Despite denials by the Iranian government, U.S. trade sanctions have hurt Iran through the loss of oil sales and a shortage of hard currency, administration officials said Wednesday.

But a high-ranking official of the Central Intelligence Agency told the Senate Banking Committee that in the long term, the U.S. trade embargo would not have a major effect on Iran unless the sanctions get strong backing from other countries. "We believe this backing will be difficult to obtain," said John Gannon, the CIA's deputy director for intelligence.Committee Chairman Sen. Alfonse D'Amato, R-N.Y., said the sanctions were

helping but that more needs to be done to rein in Iran, stop its funding of global terrorism and end its nuclear-weapon program. Sen. D'Amato has introduced legislation that would extend the embargo by imposing sanctions on foreign companies dealing with Tehran.

In response to questions from Sen. D'Amato and Sen. Lauch Faircloth, R- N.C., the administration officials said there was evidence Iran was continuing to export terrorism around the world, but refused to discuss in public the possibility of any terrorist activity by Iran on U.S. soil. They also said they could only talk in a closed, classified session about specific actions against Iran by other nations.

Sen. D'Amato promised the administration officials he would not seek a vote on the bill by the full Senate without giving the White House ample notice, but said he would not entirely drop work on the measure. Instead, he will try to add more of his Senate colleagues to the bill's list of co-sponsors, a move he said would pressure U.S. allies by showing the bill had strong support.

The bill is opposed by the administration because it could backfire, ''hurting American businesses and harming the American economy," said Peter Tarnoff, undersecretary of state for political affairs.

Mr. Tarnoff said some countries are already quietly supporting the U.S. sanctions with actions of their own.

"It would be a mistake for us to exaggerate the gap between our policy and that of most other industrialized nations toward Iran," Mr. Tarnoff said. ''G-7 countries refuse to engage in any nuclear cooperation with Iran, and they prohibit exports to the Iranian military of arms or sensitive dual-use technology."

Mr. Tarnoff and Mr. Gannon both pointed to Japan's decision to postpone a $460 million loan to Iran, and the French government's refusal to give official support to the French energy firm Total for its involvement in Iran's Sirri offshore-oil project.

Mr. Gannon said a number of Western governments argue that dealing with Iran will do more to moderate its behavior than would isolation.

He said nations such as Germany, Japan and Italy, which have significant loans outstanding to Iran, believe that supporting sanctions would jeopardize any payments to them by the Iranian government.

''They are also concerned that joining the ban would threaten their efforts to expand commercial opportunities for their firms," Mr. Gannon said. CIA reports give the Iranian government a "three-in-four chance to stay in power over the next three years, despite the worsening economy." He predicted, however, that as the economy deteriorates and living conditions grow harder, public unrest will increase, making it difficult for the regime to maintain stability.

The D'Amato bill would ban U.S. government purchases from any company around the world that does business with Iran, refuse U.S. export licenses for those firms, and prevent their executives from entering the United States. The administration could also use its discretion to impose import sanctions, prohibitions of export assistance and a review of mergers, acquisitions and takeovers in the United States by sanctioned companies.

A similar bill was introduced in the House Wednesday by Rep. Benjamin A. Gilman, R-N.Y., who serves as chairman of the House International Relations Committee.