WASHINGTON — Iran’s response to an incentives package aimed at defusing a dispute over its nuclear program is unacceptable, American officials said today, making the prospects of new sanctions against the country more likely.

The officials told The Associated Press that a one-page document Iran presented to the European Union foreign policy chief, Javier Solana, in Brussels is not, as had been sought, a definitive reply to the offer from major world powers to suspend uranium enrichment and reprocessing in exchange for economic and other benefits.

Instead, the officials said it was a restatement of Tehran’s earlier insistance on the right to conduct peaceful nuclear activities and essentially a transcription of portions of recent telephone conversations to that effect between Mr. Solana and the chief Iranian negotiator, Saeed Jalili.

One American official familiar with the document described it as “more obfuscation and delay” and not a “real response” to the package, which was presented earlier this year by the five permanent members of the U.N. Security Council and Germany.

The officials, who said they were not surprised by the response, spoke on condition of anonymity because Mr. Solana’s office has not yet characterized the Iranian reply.

In Brussels, an E.U. diplomat said the Iranian response would be analyzed and discussed “very soon” by Mr. Solana and senior diplomats from the six countries that made the offer – Britain, China, France, Germany, Russia, and America.

The State Department said those diplomats would hold a conference call tomorrow to discuss the way ahead and the American officials said a discussion of new sanctions on Iran could begin as early as then.

Shortly after Mr. Solana’s office received the document and forwarded copies by e-mail to the six governments involved, the department said that anything less than full acceptance of the package would force the grouping, known as the P5-plus-1, to seek new sanctions against Iran.

“We are looking for a clear, positive response from Iran, and in the absence of that we’re going to have no choice but to pursue further measures against them,” a spokesman, Gonzalo Gallegos, said.

The offer was reiterated to Iran on July 19, when senior diplomats from the six nations and the European Union met in person with Mr. Jalili to set an informal two-week deadline for Iran to either accept or reject it.

The meeting was notable because the Bush administration broke with its long-standing policy and sent the third-ranking State Department diplomat to the session aimed at proving its seriousness about the package.

America and others accuse Iran of trying to develop nuclear weapons under cover of a civilian atomic energy program. Iran denies the charge, insisting its program is peaceful, but it has thus far refused to halt enriching uranium, which can produce the ingredients for a bomb.

Iran is currently under three sets of U.N. Security Council sanctions and could soon face a fourth unless it accepts the incentives package. In addition, America, the European Union, and individual E.U. members have imposed their own unilateral sanctions against Iranian banks and other institutions.