A former Iranian leader once seen as the harbinger of moderation and better relations with the United States is making the case for dialogue nearly on the doorstep of the White House.

Mohammed Khatami is the most senior Iranian to visit the capital since Islamic fundamentalists seized the U.S. Embassy in Tehran in 1979 and held Americans hostage for 444 days.

President Bush and his administration are not giving Khatami a warm reception, although the U.S. government is providing and paying for security agents for the former Iranian president. The administration has sworn off serious contact with the Islamic government for now and is pushing for economic penalties over Tehran's disputed nuclear program.

The centerpiece of Khatami's visit to Washington was an address and news conference Thursday at Washington National Cathedral, a few miles (kilometers) from the White House.

The stop coincides with what may be a turning point in the long and largely fruitless international effort to deny Iran technology and expertise that the West fears could lead to a nuclear weapon.

If the United States gets its way, world powers could vote in the next few weeks to impose the first in a series of punishments intended to further increase pressure on Iran to roll back its nuclear development program.

Iran claims its program is aimed only at generating nuclear energy. The nuclear program, begun in secret nearly two decades ago, has become a point of national pride for Iran and its hard-line president, Mahmoud Ahmadinejad.

Diplomats from the countries that have offered to bargain with Tehran were meeting Thursday in Berlin to discuss the next step now that Iran has defied a U.N. deadline to shelve uranium enrichment activities. In different forms, enriched uranium can be used either for nuclear energy or weapons.

The State Department granted Khatami a visa to visit the United States for a two-week speaking tour. Approval came despite the long-standing enmity between the two countries as well as severe trade and other penalties the United States imposed on Iran after the 1979 revolution.

Khatami ran for office as a reformer but was unable or unwilling to carry out many of his programs during two terms in office from 1997 to 2005. Hard-liners blocked some Khatami proposals, including more press freedoms, that had encouraged the United States and other democracies.

State Department spokesman Sean McCormack said Khatami will not meet with any U.S. officials. The trip has angered some conservatives in Congress, some influential Iranian exiles in the United States and some of the U.S. diplomats and employees held captive a quarter-century ago.

"President Khatami is here on a private visit," McCormack said at the start of the Iranian's five-city tour. "He is not here at the invitation of the United States government, he is here at the invitation of the United Nations and then some private United States organizations. Private U.S. citizens wanted to have this interaction with him."

The administration allowed the visit to demonstrate good will toward Iranians in general, if not their leaders, and to point up the free speech and freedom of movement that are possible in the United States. Before Khatami arrived, McCormack said he hoped the universities and others hosting Khatami would ask him tough questions.

The dean of Harvard University's John F. Kennedy School of Government defended the decision to invite Khatami to speak on the eve of the fifth anniversary of the Sept. 11 attacks.

"Do we listen to those that we disagree with, and vigorously challenge them, or do we close our ears completely?" Dean David Ellwood said in an interview published Thursday in The Boston Globe.

Ellwood said he approved the invitation, first proposed by faculty after they learned Khatami would be speaking at the United Nations.

This Sunday, one day before the anniversary of the terrorist attacks, was the only date available, the dean said.

In interviews with U.S. media this week, Khatami has said Iran is still interested in negotiating over its nuclear program and asked for patience. He said the West's offer has not been rejected.