Secretary of State John Kerry said Thursday that Iranian President Hassan Rouhani's overtures to the West have been "very positive" but sounded a note of caution.
"Everything needs to be put to the test," Kerry said of comments Rouhani made in an interview with NBC News, declining to give a timetable for when President Obama might meet with him
"We'll see where we go," he said. "And at the right moment, I think that the White House and the State Department will make clear where we are headed."
Rouhani and Obama will be in New York next week for the United National General Assembly, but no meeting is scheduled.
White House spokesman Jay Carney said Thursday that Obama is willing to meet with Rouhani whenever the Iranians show they are serious about giving up their disputed nuclear weapons program.
"It's possible," he said of a face-to-face in the near future. "But it has always been possible."
In his first international interview since his election, Rouhani gave NBC News' Ann Curry new indications that he's anxious to resolve the impasse over his country's atomic program and has the political backing to cut a deal — underscoring his reputation as a pragmatic moderate.
But in the interview, the cleric also called Israel a "warmongering" occupier and sidestepped a question on whether he agrees with his predecessor, the incendiary Mahmoud Ahmadinejad, that the Holocaust is a myth.
Analysts said he is trying to straddle two political realities: the need to engage the West and negotiate a deal to end crippling economic sanctions and the powerful role that hardliners play at home.
"He’s in a delicate position," Geneive Abdo, a fellow at the non-partisan Stimson Center.
Suzanne Maloney, a fellow in the Saban Center for Middle East Policy at the Brookings Institution, said the contrast between Rouhani and Ahmedinejad had led to a touch of "irrational exuberance."
On Capitol Hill, there was a call for Rouhani to move beyond promising comments on subjects ranging from Syria to citizen freedoms.
"Actions speak louder than words," House Speaker John Boehner said.
Sen. Kelly Ayotte (R-N.H.) said Obama should not sit down with Rouhani during the U.N. General Assembly next week without preconditions.
"I believe – as Prime Minister Netanyahu has warned — that he’s a wolf in sheep’s clothing and that this is not in fact a new tack in leadership from the Iranians, or that there really does exist a moderate there," she said.
House Minority Leader Nancy Pelosi said she hopes that Rouhani's middle-of-the-road words are "not just a public relations campaign" as Israel's Netanyahu has argued, but struck a more hopeful note.
"We're all looking forward to his speech to the United Nations, to perhaps a meeting with the president," she said. "I don't know if that's a reality. But again, any engagement, any diplomatic efforts are welcome."
In Wednesday's interview, diplomacy took a back seat when Rouhani was asked about Israel; he called it a "usurper government" that "does injustice to the people of the region, and has brought instability to the region, with its warmongering policies."
Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace, said that was to be expected.
“The rejection of Israel's existence has been one of Iran's ideological principles since the 1979 revolution,” Sadjadpour said. “It will be very difficult for Rouhani to substantively change this policy, but he can refrain from being gratuitously hostile, like Ahmadinejad.
“Iran's hard-liners wish death to Israel. Iran's moderates merely wish Israel terminal illness.”
Rouhani did avoid the "virulent rhetoric" that Ahmedinejad and other Iranian leaders have used to talk about Israel, and withholding all criticism would have made him sound two-faced, Maloney said.
"There's always a concern that Iranians will speak with one voice to the West in order to win approval here and erode the international community's will to impose sanctions," she said.
She said she was "disappointed" that Rouhani did not take the opportunity to disavow Ahmedinejad's previous denials of the Holocaust — just days after his foreign minister tweeted Rosh Hashana wishes. He simply said he was not "a historian."
Abdo said it would have been remarkable if he had acknowledged the Holocaust.
"That's off the table," she said, adding, "We should not assess the degree of change in Iran based on their views on Israel."
Reacting to the interview, the Israeli prime minister's office said Rouhani had not distinguished himself from Ahmadinejad on nuclear weapons, Israel or the Holocaust.
"You don't need an historian in order to recognize the being of the Holocaust," it said in a statement. "You need to be a human being."
NBC News' Andrea Mitchell, Paul Goldman, Carrie Dann, Tom Curry and Frank Thorp contributed to this report.