Iran's Supreme Leader Ayatollah Ali Khamenei's on Tuesday warned against the US imposing its will on negotiations with Teheran.
Khamenei's statements come as Iran is asking to modify a UN-brokered proposal for Russia and France to turn the Islamic republic's uranium stockpile into nuclear fuel and allay Western fears over a possible weapons program.
"Whenever the US offers a smile, it hides a dagger in his back," said Khamenei according to the state news agency. He rejected "talks in which the US decides about its results in advance."
US Secretary of State Hillary Rodham Clinton said Monday in Marrakech that the UN nuclear deal could not be altered.
Khamenei's statements came the day before annual anti-American demonstrations for the 30th anniversary of the 1979 storming of the US embassy - traditionally a time for speeches slamming Washington.
The US and its western allies fear that Iran's nuclear program is geared toward producing a weapon, while Tehran maintains it is for peaceful purposes.
Khamenei said that even as the US talks about negotiations with Iran, it is threatening it.
"American talk about negotiations on one hand but on the other they continue their threats and say how negotiations must reach their own desired conclusion."
Khamenei also slammed what he called "the new US president's beautiful words," which are not supported by deeds, referring to several messages directed by US President Barack Obama to the Iranian people.
Khamenei, who has final say in all state matters, also urged the US not to pin its hopes on the Iranian opposition, who are calling for better ties with the West, describing them as "few" and "naive."
Even as Khamenei dismissed the opposition, however, a possible showdown is looming over Wednesday's annual anti-US demonstration as reformists have called for anti-government protests.
The demonstrations would be a display of resolve by the opposition against Ahmadinejad's crackdowns since his disputed re-election in June, but authorities have said they will not tolerate any disruptions to Wednesday's events.
The state-run Islamic Republic News Agency quoted the head of Teheran's security forces, Gen. Ali Reza Alipour, as saying that police will use all their "power and capacity" to confront any demonstrators.
