Thousands of Iranians chanting "Death to America" marked the anniversary on Friday of the 1979 seizure of the U.S. embassy amid references to recent U.S. allegations of an Iranian assassination plot.

The annual celebration in front of what Iranians call "the den of spies" was also used this year as a platform to hail the Arab Spring -- termed the "Islamic awakening" here -- and to denounce Israel.

Four elderly U.S. men sat in federal court in the southern state of Georgia Wednesday facing accusations that they were far-right militia members intent on attacking U.S. government offices and plotting targeted assassinations.

The men, ranging in age from 65 to 73, were arrested by FBI agents Tuesday on charges "relating to plans to obtain an unregistered explosive device and silencer and to manufacture the biological toxin, ricin," the Justice Department said.

The White House said Wednesday, after the Arab League revealed Syria had agreed to a plan to end political violence, that it had not changed its position that President Bashar al-Assad should go.

White House spokesman Jay Carney did not comment on the details of the Arab League plan or on whether Washington had been informed of the Syrian response.

The White House said Wednesday it was "deeply disappointed" that Israel decided to speed up settlement building after UNESCO decided to admit the Palestinians, boosting their statehood drive.

"We are deeply disappointed by yesterday's announcement about accelerated housing construction in Jerusalem and the West Bank," said White House spokesman Jay Carney.

EU foreign policy chief Catherine Ashton urged Israel on Wednesday to backtrack on its decision to accelerate building of new settlements in response to Palestinian accession to UNESCO.

"I am deeply concerned by the latest Israeli decisions to expedite settlement activities in response to Palestinian accession to UNESCO," Ashton said in a statement.

Even as Europe's debt crisis spirals out of control, Wall Street is casting an eye on a fast-approaching congressional deadline that could spark a debt crisis this side of the Atlantic.

U.S. investors -- for weeks preoccupied with the tumult raging in Greece and the broader Eurozone -- are starting to look with trepidation at the November 23 deadline for a Congressional committee to agree to $1.2 trillion in deficit cuts.

Four U.S. men were arrested on Tuesday for plotting to attack government workers and official buildings, and for trying to manufacture the deadly biological toxin ricin, authorities said.

"These defendants, who are alleged to be part of a fringe militia group, are charged with planning attacks against their own fellow citizens and government," said Sally Quillian Yates, U.S. Attorney for the Northern District of Georgia.

Saudi Crown Prince Nayef bin Abdul Aziz on Tuesday noted that U.S. allegations of Iranian involvement in a plot to murder the Saudi ambassador to Washington did not "require an agreement" with Tehran concerning its hajj pilgrims, Agence France Presse reported.

AFP quoted the prince earlier on Tuesday as saying that "there can be no compromise with Iran concerning the assassination bid because there is no need for it." However, the agency later corrected that version, noting that it had misinterpreted the crown prince’s remarks.

Russia could take steps of "a technically military nature" if its objections to NATO's planned missile defense system are not heeded, Russian Foreign Minister Sergei Lavrov told a Serbian daily Tuesday.

"If our partners in the future continue to ignore out position we should protect our interests by other means... Concrete measures might be needed... a response of a technically military nature," Lavrov told Belgrade's Vecernje Novosti in an interview published Tuesday.

Iran has sent a letter to the United States seeking an "apology" over allegations of an Iranian assassination plot on U.S. soil, foreign ministry spokesman Ramin Mehmanparast said Tuesday.

"A letter has been sent... It is our right to seek the official apology of the Americans in protest of this made-up scenario as these allegations are not true at all," Mehmanparast told a news conference, quoted by the official IRNA news agency.