Russian President Vladimir Putin says that the United States' move to impose "unilateral" sanctions against Iran will result in "harmful" consequences.

Putin made the remarks while addressing a session of the St. Petersburg International Economic Forum (SPIEF) with his French counterpart Emmanuel Macron on Friday.

He warned of US President Donald Trump's decision to withdraw from a multilateral nuclear agreement, officially known as the Joint Comprehensive Plan of Action (JCPOA), signed between Iran and major powers in 2015 and made it clear he did not agree with the decision.

The Russian president emphasized that "unilateral" steps taken by countries like the United States led to a "dead-end and were always counterproductive."

President Trump announced on May 8 that Washington was walking away from the nuclear agreement which was reached between Iran and the five permanent members of the UN Security Council - the US, Britain, France, Russia and China - plus Germany.

Trump also said he would reinstate US nuclear sanctions on Iran and impose "the highest level" of economic bans on the Islamic Republic.

Iran has said it would remain in the JCPOA for now, pending negotiations with the other signatories in the coming weeks before making a final decision on its future role in the agreement. Tehran wants the Europeans to give it clear-cut guarantees about fulfilling their obligations if it remains in the accord.

Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei said on Wednesday US enmity toward Iran is deep but all American plots against the country have failed since the victory of the Islamic Revolution.

Elsewhere in the forum, Putin said Washington's flip-flopping on international agreements after the election of new US presidents generated mistrust.

He slammed the "unacceptable" move by the US to apply its own rules beyond its borders.

"We need to put an end to that, this is unacceptable," Putin said.

He added that everyone will lose if the JCPOA falls apart and said it was still possible to save the nuclear deal despite the US withdrawal from it.

"The US president is not closing the door on negotiations. I think that all is not yet lost," the Russian leader said.

Putin expressed Russia's readiness to hold dialogue with the US, however, emphasized that a proposed summit with Trump was beset by problems.

The US president in March invited his Russian counterpart to meet at the White House. However, ties between Washington and Moscow have deteriorated further over a number of issues. 

"We are ready for dialogue with Trump. [But] for now it's not working out. Many problems are arising," Putin told the forum.

France hopes Trump will return to Iran nuclear talks: Macron

The French president, for his part, commended "direct and frank" talks with his Russian counterpart on different issues and expressed hope that Trump would return to Iran nuclear negotiations.

Macron added that French companies would have to decide for themselves how to react to fresh US sanctions against Iran.

The French leader noted that he had a duty to continue working with the US president and said even if there are "issues on which we have differences," he has strong relationship with Trump.

US Secretary of State Mike Pompeo said on Monday that Washington will increase the financial pressure on Iran by imposing the "strongest sanctions in history" on the Islamic Republic if Tehran refuses to change the course of its foreign and domestic policy.

Speaking weeks after the United States' pullout from the nuclear agreement Iran signed with major powers in 2015, he laid out 12 tough conditions for any "new deal" with Tehran. The conditions included withdrawal of Iran's military advisors from Syria, who have been helping the country's legitimate government in its anti-terror fight against terrorist outfits, which have been mostly aided and abetted by the US and its Western and regional allies.