Iran can overcome problems caused by "barbaric" economic sanctions that Western states have imposed over its nuclear programme, supreme leader Ayatollah Ali Khamenei said on Wednesday.

"These sanctions are barbaric. This is a war against a nation... But the Iranian nation will defeat them," Khamenei said in a speech broadcast on state television.

The all-powerful leader said the sanctions had created "problems" for the country, and that "some mismanagement" of the draconian measures was adding to those problems. He did not elaborate.

Iran's currency, the rial, has lost 40 percent of its value against major currencies in the past week, with the central bank unable to support the rial on the open market due to a lack of foreign cash.

The collapse of the rial, which has lost more than two-third of its value since the beginning of the year, has sparked a row with some politicians blaming President Mahmoud Ahmadinejad's management.

Ahmadinejad has pointed the finger at the sanctions and at the other branches of government.

In his speech, Khamenei called on officials to refrain from making accusations against each other, and urged them to restore unity to defeat the sanctions.

"This is not an issue that the Islamic republic cannot resolve. With the grace of God, the Iranian nation will overcome all these problems," he said.

Western powers have gradually tightened sanctions against Iran in the past two years, particularly against its vital energy sector, to pressure Tehran to abandon the controversial parts of it nuclear programme.

As well as hitting its currency, the sanctions have prompted a drop in Iran's oil exports and production, slowing its economy and boosting the ranks of the jobless.

The US government, which is leading the sanctions, has also pointed the finger at Iran's economic management, but said sanctions relief could quickly occur if Tehran curbed its nuclear activities.

Khamenei accused the West of "lying" over its offer to lift sanctions in return for Iran furnishing guarantees to back its claims its atomic programme is intended for civilian purposes only.

The West suspects Iran is seeking a nuclear weapons capacity, despite repeated denials from Tehran.

In addition to the punitive measures, the West is involved in talks with Tehran on the nuclear impasse, but those negotiations have stalled for years.

Khamenei also rejected the notion that sanctions were linked to Iran's nuclear efforts, as the West claims they are.

"The enemies -- the US and some European governments -- are nowadays linking the sanctions to (Iran's pursuit) of nuclear energy. They are lying," he said.

The supreme leader argued that his country has been targeted by sanctions since the 1979 Islamic revolution for its "independence and resistance" against world powers.

Tehran is under several sets of international sanctions imposed by the UN Security Council.