"The Americans are definitely letting the Iranians know that they are active in going after Iran's nuclear program," said Hooman Majd, an Iranian-American journalist.
A colleague of Amiri's at Tehran University called the disappearance "a disturbing sign" and blamed the Saudis for helping the U.S., according government-approved English-language web site Press TV.
"The Saudi regime has effectively discredited itself and will be seen by those who know what has gone on in the region as being confined to American demands and effectively abiding by American wishes," said Mohammad Marandi, a Tehran University professor, according to the Iranian web site.
On Tuesday, President Obama said that he wanted sanctions against Iran "this spring."
"I'm not interested in waiting months for a sanctions regime to be in place," said Obama. "I'm interested in seeing that regime in place in weeks."