Russian President Vladimir Putin has confirmed that he will visit Iran, despite reports of a possible plot to kill him there.
Vladimir Putin is due to arrive in Iran on Monday evening
"Of course I'm going," Mr Putin told a news conference, ending earlier uncertainty about the visit.
But Iran's presidential office later said Mr Putin would arrive on Tuesday instead of Monday as planned.
Russian media quoted unnamed security sources as saying suicide bombers were plotting to kill Mr Putin in Tehran.
Iran's foreign ministry dismissed the reports as "completely baseless".
Mr Putin is due to attend a summit of Caspian Sea heads of state on Tuesday.
He would be the first Russian leader to visit Iran since Soviet dictator Joseph Stalin went there in 1943.
Mr Putin said he would discuss Iran's controversial nuclear programme with Iranian leaders. "It is futile to frighten Iran and its people. They are not scared," Mr Putin said.
He called for a peaceful resolution of the dispute over Iran's nuclear research and urged the international community to show patience in the matter.
He was speaking at a news conference in Wiesbaden, Germany, following talks with German Chancellor Angela Merkel.
The US accuses Iran of seeking to develop nuclear weapons - but Iran insists its programme is entirely peaceful.
Mrs Merkel said Iran must show "greater transparency" on the nuclear issue and abide by UN resolutions. "In our view it's also clear that if the Iranian leadership does not do this, then there must be a round of new sanctions," she said.
Mr Putin's spokesman Dmitry Peskov confirmed that the earlier uncertainty about the president's visit to Iran was linked to the alleged assassination plot.
"These reports were very serious but I can't give you any detail on the nature of what our security services found out because it's all very sensitive", he told the BBC.
Later Iranian President Mahmoud Ahmadinejad's office said Mr Putin had left Germany for Moscow and would arrive in Tehran on Tuesday.
The Kremlin press service refused to say when Mr Putin would arrive.
Interfax news agency said that according to Russian security service sources, several groups of suicide bombers had been preparing for an attack in Tehran.
The services had relied on information received from several unnamed sources outside the country, the agency said.
Meanwhile, Mr Hosseini said the reports were "part of a psychological war waged by enemies to disrupt relations between Iran and Russia".
"Such erroneous reports will have no effect on the programme already decided upon for Mr Putin's visit to Tehran," he said.
Correspondents say Moscow and Tehran have good relations. Russia is helping to build the controversial Bushehr nuclear power plant in southern Iran.
A member of the Russian parliament's security committee, Gennady Gudkov, said the assassination plot reports were likely to have a "fairly high level of reliability".
"There are enough radical organisations, forces and movements of an extremist nature, oriented against Russia, which would like to settle a score with the Russian president," he told the state-owned Russian news channel, Vesti TV.
"There are certainly organisations of this kind in Tehran," he said.
Russian officials have said several plots to assassinate Mr Putin on foreign trips have been uncovered since he became president in December 1999.
Shortly after his election, Ukrainian security services said they had foiled an attempt to kill Mr Putin at an informal summit of former Soviet republics in the Black Sea resort of Yalta.
In 2003, police in London said they had arrested two men in connection with another plot to assassinate him.