The nuclear reactor in the southern town of Bushehr would go ahead despite resistance from the United States and Israel, he said on Sunday during a visit to the Central Asian former Soviet republic of Tajikistan.
"Thankfully, despite all the pressure that is being put on Russia from all sides - including that from the United States - Russia has bravely declared that it is ready to cooperate with Iran," Khatami told reporters.
"We feel that our cooperation strengthens the whole region, makes it more stable," he said. His comments came amid apparent efforts by Russian officials to slow down the construction of the Bushehr nuclear power plant amid Western worries over the project.
At the earliest, the plant's launch has been delayed until next
year. Khatami arrived in Tajikistan for talks over a $400-million-project to complete a hydro-electric power station that was launched 15 years ago but never completed.
Earlier on Sunday, Iran rejected demands by Europe's three major powers to abandon its uranium enrichment programme.
Foreign Ministry spokesman Hamid Riza Asifi said Iran already had the technology required for its nuclear fuel cycle and it would not reverse the situation.
"We feel that our cooperation (with Russia) strengthens the whole region, makes it more stable"
"If the demand is that we don't master nuclear technology for peaceful purposes, it's out of the question because we have reached that point," Asifi said.
"But if Europeans want assurances that we only make peaceful use of nuclear energy, we are ready to give guarantees," he added.
He said the guarantees Tehran was prepared to offer would be within the framework of the additional protocol to the Nuclear Non-proliferation Treaty.
"We are ready to give any sort of guarantees within the framework of the additional protocol," he said.
According to a confidential document made available to the media on Saturday, Britain, France and Germany have set a November deadline for Iran to meet certain conditions meant to banish concerns that it is secretly trying to make nuclear weapons.
Asifi: Tehran willing to guarantee
peaceful use of nuclear energy
Prepared for Monday's start of a key meeting of the International Atomic Energy Agency, the document proposes a "trigger mechanism", warning of possible "further steps" - which diplomats defined as shorthand for referral of Iran's case to the UN Security Council and possible subsequent sanctions.
The document brings the three European countries closer to the US position on what to do about Iran's nuclear programme. Washington insists Tehran is covertly trying to build a nuclear bomb.
Up to now, the three European countries have resisted US attempts to have Iran brought before the Security Council.