Five permanent members of the UN Security Council and Germany are considering new sanctions against Iran after the Islamic republic failed to give a positive response to suspend its controversial nuclear program, the State Department said Monday.

Iran's chief nuclear negotiator Saeed Jalili (L) smiles before a meeting on nuclear issues with U.S. Undersecretary of State William Burns (R) and E.U. foreign policy chief Javier Solana (not pictured) at the Town Hall in Geneva July 19, 2008.[Xinhua/Reuters Photo]

"We are disappointed that we have not yet received a response from Iran," State Department spokesman Gonzalo Gallegos told reporters after representatives of the United States, Britain, France, Russia, China and Germany spoke by telephone conference over Iran's nuclear issue earlier in the day.

"We agreed in the absence of a clear, positive response from Iran (that) we have no choice but to pursue further measures against Iran," Gallegos said

The telephone conference was held after Iran's top nuclear negotiator Saeed Jalali told European Union foreign policy chief Javier Solana that his country would deliver a written response to the incentives package aimed at getting it to halt sensitive atomic activity on Tuesday, Gallegos said.

The spokesman declined to say if sanctions would be pursued if Iran accepted the offer then.

Solana and Jalali held nuclear talks in Geneva on July 19 over Tehran's disputed nuclear program.

The United States, in a break with past policy, took the unprecedented step of sending Undersecretary of State William Burns to meet Iran's chief negotiator at the talks.

During the one-day meeting, Iran failed to give a clear answer to the package of incentives. However, both Solana and Jalili said the meeting was positive and constructive and promoted understanding of each other's positions. They also agreed to talk again by phone or in person in about two weeks.

The United States accuses Iran of developing secretly nuclear weapons under the cover of civil nuclear program. Iran denies the charges.