President Obama will not meet with Iranian President Hassan Rouhani on the sidelines of the United Nations General Assembly, after the Iranians turned down an offer from the United States, according to a White House pool report.

Iranian President Hasan Rouhani shakes hands with French President Francois Hollande during the 68th session of the United Nations General Assembly at United Nations headquarters Tuesday, Sept. 24, 2013. (AP Photo/Craig Ruttle)

Senior administration officials said the White House offered "an encounter" -- not an official meeting but still a conversation -- but that the Iranians said it is "too complicated for Iranians to do at this point."

"We have said publicly, and we also said privately to the Iranians, that we're open to having discussions on the margins of UNGA -- informal discussions not a bilateral meeting," said a senior administration official. "That proved to be too complicated for the Iranians to do at this point."

Another official said: “I think the takeaway ... is the Iranians, No. 1, have an internal dynamic that they have to manage. And the relationship with the United States is clearly quite different than the relationship that Iran has with other Western countries even."

The meeting would have been the first of its kind since 1977.

Secretary of State John Kerry will still engage in the first talks between top officials in the United States and Iran since 1979 when he meets with Iranian Foreign Minister Javad Zarif and other leaders to talk about Iran's nuclear policy.

In a joint statement, GOP Sens. John McCain (Ariz.), Lindsey Graham (S.C.) and Kelly Ayotte (N.H.) said talks are fine, but that they remain "deeply skeptical" about Iran's real motivations.

"We need to approach the current diplomatic initiative with eyes wide open, and we must not allow Iran to use negotiations as a tool of delay and deception," the senators said in a statement. "A real negotiation does not mean that the diplomats talk while the Iranians enrich."