Iran's response did not rule out such a mission in the future but deputy department spokesman Adam Ereli said the US offer had been based on the current severity of the situation on the ground in the devastated city of Bam and might no longer be valid as conditions there improve.

"We have heard back from the Iranians that, given the current situation in Bam and all that is going on there now, it would be preferable to hold such a visit in abeyance," Ereli told reporters.

"Therefore, we are not pursuing this further at the moment," he said.

Asked whether Iran had said such a visit might be acceptable in the future, Ereli stressed that the US proposal had been intended to demonstrate "our compassion for the Iranian people and to provide humanitarian support for their efforts to recover from last week's tragic earthquake."

Once that recovery is well underway or complete, a US humanitarian mission to Iran might no longer be necessary, he suggested.

"The situation is evolving on the ground, so the utility of such a visit further in the future is really a matter of speculation," Ereli said.

Washington approached Tehran earlier this week through its ambassador to the United Nations about the possibility of sending a delegation headed by Senator Elizabeth Dole to the "axis of evil" nation.

The United States also suggested that a member of President George W. Bush's family might accompany Dole to show the importance he places on relief for the victims of the quake, which killed some 30,000 people, a senior US official said.

Iran replied to the proposal through its UN ambassador on Thursday in language that the official paraphrased as: "Now is not a good time, maybe later."

Ereli said Washington understood the Iranian response and that the United States would not do anything that would compromise the humanitarian response to the quake survivors, about 40,000 of whom have been left homeless and are sleeping in tents.

"We don't want to do anything that makes that more difficult," he said. "We want to help and so we respect their wishes."

He added that US assistance would continue to flow into Iran and that more than 1,000 tents would be arriving in the country over the weekend.

Dole, a Republican from North Carolina, is a former secretary of labor and transportation and is married to former Senate majority leader and 1996 Republican presidential candidate Bob Dole.

Had the mission proceeded, it would have been the first public official US visit to the Islamic nation since the 1979-1981 period, when 52 Americans were held hostage in Iran for 444 days and the two countries broke diplomatic relations.

US officials stressed that the mission would have been humanitarian and not diplomatic in nature but the proposal came amid new US overtures to Iran in the aftermath of the earthquake.

In addition to the offer of assistance last week, the Bush administration on Wednesday temporarily eased US restrictions on sending money and sensitive equipment to Iran.

Bush said on Thursday that the moves were a sign of compassion and not a message that he wants warmer ties with Iran, which he labeled as part of an "axis of evil" in 2002.

"What we're doing in Iran is we're showing the Iranian people (that) the American people care, that they've got great compassion for human suffering," the president told reporters in Texas.

And he made clear that if the Islamic republic wants better relations, it must turn over any followers of Osama bin Laden it has in custody, abandon its pursuit of nuclear weapons and embrace democratic political reform.

Iranian President Mohammad Khatami has stressed that any US humanitarian help, while welcome, was not indicative of warming diplomatic relations between the two nations.

Iran's foreign minister, Kamal Kharazi, on Thursday hailed the easing of sanctions as "positive" but said that only their total lifting would create a new climate between Tehran and Washington.

TERRA.WIRE