TEHRAN, Iran — Iran’s supreme leader warned Western governments today of a “negative impact” on relations over what he called their meddling in Iran’s post-election riots, state television reported.

Ayatollah Ali Khamenei’s comments reflect continued efforts by the regime to blame Western powers such as the U.S. and Britain — not internal anger — for unrest following the country’s disputed presidential election. They also come one day after the American vice president said the U.S. is still open to negotiating with Iran over its nuclear program.

“Some leaders of Western countries at the level of president, prime minister and foreign minister openly intervened in Iran’s internal affairs that had nothing to do with them. Then, they said they don’t intervene in Iran’s internal affairs,” the television quoted Khamenei as telling thousands of Iranians during a ceremony to commemorate a revered Shiite saint.

Iran quashed street protests following its disputed June 12 election, and the leadership has been trying to erase any lingering doubts about the legitimacy of President Mahmoud Ahmadinejad by portraying the unrest as sparked by foreign meddling.

Reformist opposition leader Mir Hossein Mousavi has said the government stole the election results and that he was the rightful winner of the vote. Khamenei has sided with Ahmadinejad.

While the regime has managed to silence the protests, the continued opposition being voiced by reformist politicians and their allies through has produced a rare challenge in a country where the supreme leader’s word is supposed to be final.

Khamenei said Iran will pay attention to the remarks and behaviors of Western governments and said that it will definitely have a negative impact on future relations with Iran.

“These governments must be careful of their hostile remarks and behaviors because the Iranian nation will” react, the television quoted Khamenei as saying. “We will calculate the interventionist remarks and behaviors of these governments. Definitely, it will have a negative impact on future relations with the Islamic Republic of Iran.”

Khamenei once again emphasized his support for Ahmadinejad, calling his re-election a “lasting and pure truth.”

In France, President Nicolas Sarkozy said his country stands by Britain amid tensions with Iran over the post-election unrest. In a joint news conference with the French leader, British Prime Minister Gordon Brown said today that “the Iranian regime must be clear that we will act together with our European partners.”

But Brown insisted that the outcome of the Iranian election is a matter for the Iranian people.

In the post-election fallout, Iran detained more than a thousand protesters, along with hundreds of activists, journalists and bloggers. While most of the protesters have been released, dozens of prominent political activists remain in jail on vague charges of “acting against national security.”

Reformist Web site Norooznews said late Sunday that Hamid Maddah Shourcheh, a member of Mousavi campaign office in the northeastern Iranian city of Mashhad died of torture during detention.

Shourcheh was “martyred as a result of wound inflicted during detention,” Norooznews said, adding that he was arrested after holding a sit-in in a Mashhad mosque to protest the election results.

Along with the other arrests, Iranian authorities also detained nine local employees of the British Embassy, leading to vocal protests from Britain and the European Union.

Britain’s Foreign Office said today that Iran has released another British Embassy staff member, leaving one employee still in custody.

Ayatollah Ahmad Jannati, a close aide to Khamenei, said Friday that Iran would put detained local employees of the British Embassy on trial for inciting post-election protests, in a further effort to prove foreign elements were behind the unrest.

Hossein Rassam, a political analyst at the embassy, still remains in detention, according to his lawyer Abdolsamad Khorramshi. Khorramshi said Saturday that his client has been charged with “acting against national security.” Britain has dismissed claims of intervention as baseless.

President Barack Obama’s administration, which has made an effort to reach out to Iran since taking office, has left the door open to talks.

In an interview on ABC’s “This Week,” Vice President Joe Biden Sunday said the U.S. offer to negotiate with Tehran on its nuclear program still stands. Some thought the administration’s approach might change in light of the Iranian government’s harsh post-election crackdown.

“If the Iranians respond to the offer of engagement, we will engage,” Biden said.

Biden also signaled that the U.S. would not stand in the way should Israel opt for military action to eliminate Iran’s nuclear facilities, saying Washington “cannot dictate to another sovereign nation what they can and cannot do.”

Israel considers Iran its most dangerous adversary and is wary of Ahmadinejad. Israel and the U.S. accuse Iran of seeking to develop weapons under the cover of a nuclear power program, a claim Iran denies.

Iranian police have said that 20 “rioters” were killed during the violence, as well as eight members of the Basij militia tasked with putting down the protests.

Despite the crackdown, Mousavi and his backers insist the election was won by fraud — claims Iranian authorities say are aimed at destabilizing the country.