Iran's Supreme Leader Ayatollah Ali Khamenei said any future talks with the U.S. will only deal with issues related to the nuclear deal reached with world powers, and not any other areas.
In a statement on his website Wednesday, Khamenei said, "We approved talks with the United States about nuclear issues specifically. In other areas, we did not and will not allow negotiations with the U.S."
Negotiations on other issues would only provide an opportunity for the U.S. to "influence Iran and impose their will," the ayatollah was quoted as saying.
The nuclear deal reached in July between the U.S., Iran and five major world powers was seen as a possible catalyst toward improving Iran's long-hostile ties with Washington and its allies.
Though, thanks to the nuclear talks, it has now become almost commonplace for senior U.S. and Iranian leaders to meet publicly, neither side has taken any step toward normalizing diplomatic ties that have been severed since 1980.
Iranian President Hassan Rouhani, who is seen as a moderate in comparison to the ayatollah, said Tuesday that Tehran was ready to hold talks with the U.S. on ways to resolve Syria's civil war.
Khamenei's comments on Wednesday are seen as a possible response to that comment.
The Iranian government supports Syrian President Bashar al-Assad, who is opposed by the U.S. The two sides also disagree on a series of other regional issues, including Israel and the civil war in Yemen.
The nuclear deal, however, removes a major obstacle toward improving relations, since it will result in the end of international sanctions that have devastated Iran's economy for years.
Hardliners in each country oppose the nuclear pact and have worked to scuttle it.
On Tuesday, U.S. Senate Democrats secured a major victory in their battle to get the deal passed through Congress, when three more senators came out in favor of the agreement.
At least 42 senators now support the deal. That is enough to prevent a disapproval resolution from being passed in the Senate. President Barack Obama already had said he would veto any disapproval measure.
Republicans hold a large majority over Obama's Democratic party in the House of Representatives. The House is expected to pass a resolution opposing the Iran deal -- but without Senate support it will amount only to a symbolic gesture.
Still, the debate has given critics a further chance to voice their complaints about the agreement.
Opponents see the deal as too friendly to Iran by leaving much of its nuclear program in place while unlocking billions of dollars that some fear will be used to support terrorism.
The U.S. and its allies have long suspected that Iran was using that program to build nuclear weapons - a charge Tehran denies.
Britain and France reopened their embassies in Tehran following the nuclear deal and other European countries have sent high level delegations to talk business. Diplomatic ties between the U.S. and Iran, however, remain cut, as they have been since 1979.
Former Iranian diplomat Mehrdad Khonsari told VOA he believes that the language the Khamenei uses is part of a balancing act between “hardliners” and “moderates.”
“His latest comments are essentially to appease the hardliners, without really trying to prevent the government from pushing ahead with the agenda it has (pursued) since it came to power,” Khonsari said.
Former Iranian president Abolhassan Bani Sadr argues that Iran's leadership would “lose its raison d'etre” (reason for being) if it suddenly started dealing normally with the U.S., after dubbing its enemies, both internally and externally, “agents” of the U.S.
Bani Sadr says Iran's leaders play a “double-faced” game, claiming to be hostile to the U.S., while secretly cutting deals with it, which include U.S. acceptance of Iran's theocratic regime and a “larger regional role,” if it abides by U.S. policies.
Edward Yeranian contributed to this report from Cairo.