Iran blames US for political crisis

Iran directly accused the United States of meddling in the deepening crisis over a disputed presidential election and broadened its media clampdown to include blogs and news websites.

However, protesters again took to the streets in growing defiance of the country's Islamic rulers.

The sweep of events - including more arrests and a call for another mass opposition march through Tehran - displayed the sharpening attacks by authorities but also the unprecedented challenges directed at the very heart of Iran's Islamic regime: its supreme leader and the cleric-run system.

Any serious shift of the protest anger toward Iran's non-elected theocracy would sharply change the stakes.

Instead of a clash over the June 12 election results, it would become a showdown over the core premise of Iran's system of rule - the almost unlimited authority of the clerics at the top.

For the moment, however, both sides appear to be using the same tactics since the disputed results showed hard-line President Mahmoud Ahmadinejad as the landslide winner.

Opposition leader Mir Hossein Mousavi called for another mass rally today in open defiance of Iran's most powerful figure, Supreme Leader Ayatollah Ali Khamenei, who has urged the nation to unite behind the Islamic state.

Authorities rounded up perceived dissidents and tried to further muzzle websites and other networks used by Mr Mousavi's backers to share information and send out details of Iran's crisis after foreign journalists were banned from reporting in the streets.

Officials also stepped up claims that foreign hands have been behind the unrest.

A statement by state-run Press TV blamed Washington for "intolerable" interference in the bloody showdown over allegations of vote-rigging and fraud. The report, on Press TV, cited no evidence.

It said the government summoned the Swiss ambassador, who represents US interests in Iran, to complain about American interference. The two countries severed diplomatic relations after the 1979 Islamic Revolution.

The US State Department this week asked Twitter to postpone a scheduled maintenance shutdown of its service to keep information flowing from inside Iran.

A State Department spokesman said Washington was withholding judgment about the election and was not interfering in Iran's internal affairs.

President Barack Obama has offered to open talks with Iranian leaders to end a nearly 30-year diplomatic freeze.