(CNN) -- U.S. President Barack Obama must speak out and declare that some of the behavior of the clerical regime in Iran is unacceptable, former Obama administration official Ray Takeyh said Monday.
Takeyh, who served as an adviser in the State Department last year and is now at the Council on Foreign Relations, told CNN's Christiane Amanpour the U.S. must also be open to negotiating some sort of deal to limit Iran's nuclear ambitions.
"You can have negotiations with Iran, as the United States has had negotiations with many adversarial countries while also at the same time disapproving on the internal practices of those regimes," he said.
Takeyh's comments came just over a week after the bloodiest clashes between pro-democracy protesters and government security forces in months, clashes that left at least eight people dead. Days after those clashes, hundreds of thousands of pro-government demonstrators held rallies in Tehran and other cities.
Those protests coincided with new tensions over Iran's nuclear program, a program the United States says is intended to build a nuclear weapon. Tehran insists its nuclear activities are for peaceful purposes alone and says it's up to the West to decide whether to accept Iran's proposals on further enriching its uranium.
U.S. Secretary of State Hillary Clinton said Monday the United States remains open to the possibility of further negotiations with Tehran, despite Iran's refusal to make significant progress towards a deal before January 1 this year, as Obama has demanded.
Clinton told reporters the U.S. is holding discussions with its partners and like-minded nations about possible new sanctions and other forms of pressure.
Takeyh said he expects the United States and its allies will try to ratchet up economic pressure on Iran, targeting in particular the Revolutionary Guard and its business interests.
"So you will begin to see intensification of economic pressure on Iran in the hope that external pressure, combined with internal pressure, will cause Iran to adjust its behavior," he said.
Takeyh added that he believes the Iranian government internally is rather weak and vulnerable and may seek some sort of agreement abroad at least to mitigate international pressure.
But he said the opposition movement in Iran is also somewhat incoherent. "It doesn't have a central nervous system. It doesn't even have an identifiable set of leaders or even a coherent ideology. It is a protest movement."
He said the longer the movement sustains itself, though, the more it will develop an ideology and a leadership.
A leading critic of the pro-democracy protesters, Professor Mohammad Marandi of Tehran University, told Amanpour that opposition leader Mir Hossein Moussavi's position has been severely weakened by the December 27 protests in Iran.
"The opposition that protested on (the Shiite Muslim holy day of) Ashura made a very major tactical mistake by being very brutal towards the police and also by carrying out these protests on a day of public mourning," Marandi said.
But one of the most fearless critics of Iran's regime, former Iranian Member of Parliament Fatemeh Haghighatjoo, rejected Marandi's assessment. She said everyone still supports Moussavi.
"The government is not able to arrest all the population in Iran", she said. "The people of Iran need fundamental change in the country and I am so optimistic that they will see this change in the country in the future."