The United States will persist for now with diplomatic overtures to Iran despite the lack of a positive response from Tehran, Defense Secretary Robert Gates said on Tuesday.
Visiting Egypt, Gates said some of Iran's statements in response to the administration of President Barack Obama had "not been very encouraging."
But he added: "We're not willing to pull the hand back yet because we think there's still some opportunity."
Obama's efforts to engage with Tehran mark a break with the policy of his predecessor George W. Bush, who once labeled Iran as part of an "axis of evil."
But Gates said any dialogue would likely develop slowly, if it happened at all. He also sounded a note of caution about the prospects of a positive response from Iran.
"I've been around long enough to see these efforts attempted before, and with no result," said Gates, a former CIA director who has worked on US national security issues since the 1960s.
"The United States goes into this with its eyes wide open," he said. "If we encounter a closed fist, when we extend our open hand, then we will react accordingly."
The Obama administration, which took office in January, hopes talks with Tehran, coupled with diplomatic pressure, can resolve differences with Iran over its nuclear ambitions. Iran says it is developing nuclear power solely to generate electricity, but the United States and other nations believe Tehran wants to build atomic weapons.
'All options are available'
Some analysts have suggested the United States could seek a broader deal, to include lifting of US sanctions in return for a change of stance from Tehran not just on its nuclear work but also its support for militant groups such as Hezbollah.
But Gates, speaking at a news conference in Cairo after meeting Egyptian President Hosni Mubarak, said Washington would not forge any secret 'grand bargain' with Tehran -- an idea that alarms US allies in the Middle East.
"Concerns out here of some kind of a grand bargain developed in secret are completely unrealistic and, I would say, are not going to happen," he said.
"The United States will be very open and transparent about these contacts and we will keep our friends informed of what is going on so that nobody gets surprised."
Obama's overtures toward Iran have raised disquiet among nations such as Egypt and Saudi Arabia, which are deeply wary of Tehran and fear they could lose out from a change in policy. Egypt does not have full diplomatic relations with the Islamic Republic.
Gates also sought to play down the idea that the United States could launch a military attack on Iran, or would favor one carried out by Israel.
"While all options are available, of course, I believe that it is important to try to address our concerns about their nuclear weapons program through diplomatic and economic pressures," he said.