Iran's President Hassan Rouhani has said that his country's ties with the United States do not have to be hostile forever and that "one day this will change".
"It is not written in stone that the relationship between Iran and the US must be hostile forever. One day this will change," he said in New York on Friday, adding that it was up to both governments to create the conditions.
The US severed diplomatic ties with Tehran during a hostage crisis after the 1979 Islamic revolution.
The people of Iran must learn to trust again, and the interlocutors must earn that trust again.
Speaking on the sidelines of the UN General Assembly annual meeting of world leaders, Rouhani said the time is not right for another phone conversation or a meeting with President Barack Obama "because of the sensitivity that still exists between the two countries".
One year ago, Obama and Rouhani came close to ending the decades-long freeze on face-to-face meetings between their countries' leaders.
Obama and Rouhani spoke by telephone for 15 minutes as the Iranian leader headed to the airport after his first appearance at the UN General Assembly.
It was the first time the presidents of the United States and Iran had talked directly since the 1979 siege of the American embassy, and the conversation was hailed as an historic breakthrough.
After being elected in June last year, Rouhani pledged to improve relations between Iran and the West.
On Wednesday, Rouhani met David Cameron, the UK prime minister, at the UN headquarters, the first time any leaders of the two countries had met met face-to-face since 1979.
Rouhani, peppered with questions about a repeat conversation with Obama at a news conference before heading home after this year's ministerial meeting, said: "Not a meeting nor a telephone call had been included in the agenda nor been planned for, ... nor intended to be a part of our visit this year to the UN General Assembly".
Rouhani said there must be substantive reasons with "high objectives" for conversations between world leaders. If not, he said, "telephone calls are somewhat meaningless".
An important first step would be for Iran and six major powers including the US to reach agreement on the country's disputed nuclear programme.
He said progress so far "has not been significant," and the pace must be speeded up if the November 24 deadline for a final agreement is to be reached.
Once there is a nuclear agreement, Rouhani said, the first step will be restoring trust between US and Iran, saying "the lack of trust" is the most important issue between the two countries.
"The people of Iran must learn to trust again, and the interlocutors must earn that trust again," Rouhani said.