Foreign Ministry spokesman Mohammad Ali Hosseini said the four are Iranian nationals, and authorities are investigating their cases.
On June 1, Bush demanded that Iran "immediately and unconditionally" release the four.
The United States has denied the four are spies or clandestine employees of the U.S. government.
On May 31, international human rights groups
called on Iran to release two Iranian-American scholars -- Haleh
Esfandiari and Kian Tajbakhsh -- and peace activist Ali Shakeri. All
three are being held on suspicions of spying or acting against state
A fourth, Parnaz Azima
a reporter with Radio Farda, a joint project of Voice of America and
RFE/RL, has been charged with disseminating propaganda and is free on
bail awaiting trial.
Amnesty International, Human Rights
Watch, and Nobel Peace Prize laureate Shirin Ebadi, among others, warn
that Iranian authorities are trying to sow fear among journalists,
writers, scholars, and activists.
Some perspectives on the U.S.-Iranian talks of May 28, 2007, as expressed to Radio Farda.
Mehrdad Khansari, a former Iranian diplomat and analyst who is based in London: "Today the talks with the U.S. have begun but that does not mean that the talks will have reached a result. The Iranian and U.S. governments need to [tell] their audiences that they are not abstaining from talking to each other."
Tehran-based journalist Mashaollah Shamsolvaezin (pictured above): "There is a necessity that has forced the two countries to accept a series of new issues; these new issues are the talks that are going to begin between the two sides and I am hopeful about its future. The U.S. is facing serious [problems] regarding the situation in Iraq, from the other side is Iran facing some threats in the Middle East that come from insecurity in Iraq and also insecurity in Afghanistan. The seriousness of talks depend on the will of both sides and it seems that both sides are determined to seriously deal with issues, therefore I see a positive perspective for the Iran/U.S.talks."
Ted Galen Carpenter, a U.S. foreign policy analyst at the Cato Institute in Washington (pictured above), says he believes the talks can help: "The United States is in a difficult position right now in that the current U.S policy in Iraq simply has not worked at all; and I think we are beginning to cast about for some alternatives and Iran can be at least modestly hopeful in that regard as long as we recognize that Iranian influence in Iraq is going to be inevitably much, much stronger than it was before."
Richard Perle, a former Pentagon official (pictured above) who lobbied forcefully for a U.S. invasion of Iraq: "I don't believe [talking to Iran will] help because I don't believe there is any interest on the part of the mullahs in Tehran in changing the behavior of the government of Iran, which has been -- and I think will continue to be -- to encourage violence and disorder in Iraq."