Russian President Dmitry Medvedev has criticised the unilateral US and EU sanctions on Iran that go beyond those approved by the UN Security Council.
He said Russia "did not agree" to any separate sanctions when it backed a joint UN resolution last week.
Meanwhile, Pentagon chief Robert Gates said US intelligence showed that Iran could be able to attack Europe with "scores" of missiles by 2020.
He added that Russia seemed to have a "schizophrenic" approach to Iran.
Moscow viewed Iran as a threat, but still pursued commercial ties with it, he told a US senate hearing in Washington.
Western powers suspect Iran is seeking nuclear weapons - which Tehran denies.
In an interview that ran on Thursday, the Russian leader criticised the EU and US for acting unilaterally.
"We didn't agree to this when we discussed the joint resolution at the UN," Mr Medvedev told the Wall Street Journal.
Russia this month agreed to back a fourth round of UN sanctions against Tehran, following months of US-led diplomacy.
"A couple of years ago, that would have been impossible," Mr Medvedev said. "We should act collectively. If we do, we will have the desired result."
The fresh EU sanctions approved in Brussels on Thursday include a ban on investments and technology transfers to Iran's key oil and gas industry - measures that go further than the latest UN sanctions.
Only a day earlier, the US announced sanctions that ban Americans from trading with a number of firms and individuals, including Iran's Post Bank, its defence minister and the air force and missile command of the Revolutionary Guard Corps.
Separately, at a senate hearing in Washington, US Defence Secretary Robert Gates said US intelligence had shown that Iran could launch an attack against Europe with "scores or hundreds" of missiles by 2020.
He said the intelligence had prompted major changes to US missile defences plans, called a "phased adaptive approach".
The new approach uses sea- and land-based interceptors to protect Nato allies in Europe, instead of larger weapons designed to counter long-range missiles.
One of the elements that contributed to the phased approach "was the realisation that if Iran were actually to launch a missile attack on Europe, it wouldn't be just one or two missiles or a handful," Gates told the hearing.
"It would more likely be a salvo kind of attack, where you would be dealing potentially with scores or even hundreds of missiles."
During the hearing, Mr Gates acknowledged one lawmaker's concerns about Russia's long-standing commercial links to Tehran, which he noted go back more than 20 years.
"You've just put your finger on a kind of schizophrenic Russian approach to this," Mr Gates told the Senate Armed Services Committee.
"I think that it is this balancing act. And Russia, they recognize the security threat that Iran presents," he said.
On 10 June the Security Council endorsed a fourth round of UN sanctions on Iran, including tighter financial curbs and an expanded arms embargo.
Iranian President Mahmoud Ahmadinejad dismissed the vote and rejected calls to halt uranium enrichment - which could have military as well as civilian uses.
Iran insists its nuclear programme is solely designed to produce energy.