Iran's finance minister on Friday warned that the West would "pay a price" for sanctions on his country over its nuclear programme, while vowing to stem a severe currency crisis.

Western powers have tightened economic sanctions against Tehran in recent years, sparking a drop in crucial oil exports and a collapse of its currency, pounding the economy and sending unemployment higher.

On Friday, finance minister Shamseddin Hosseini echoed Tehran's regular criticism of the sanctions, saying they were part of an "economic war" and warned that Western firms would suffer as Iran moves to trade with other nations.

"The sanctions are not only affecting the Iranian economy but also other countries and foreign companies," Hosseini told a press briefing in Tokyo, where he is attending International Monetary Fund and World Bank meetings.

"Turkey has now become our important trading partner in place of Germany, while China may grab the market share that Japan used to have," he added.

Hosseini also warned: "Those who imposed sanctions are to pay a price."

Talks between Iran and major powers on the nuclear impasse have stalled for years, as Tehran insists its atomic programme is for peaceful purposes while the West accuses it of working to develop nuclear weapons.

Tehran is also under several sets of international sanctions imposed by the United Nations Security Council.

Also Friday, Hosseini said measures were being taken to halt a slide in the Iranian rial.

Iran has been facing a growing shortage of foreign cash, preventing the central bank from being able to support its currency on the open market, where it has lost more than two-thirds of its value since the beginning of the year.

The punitive measures have hindered the Islamic republic's ability to repatriate much of the foreign revenues generated by its vital oil exports.

"The Iranian economy, after many years of relatively robust growth, has fallen into contraction this year," IMF Middle East director Masood Ahmed told AFP in Tokyo.

"This is due to the external shocks... the reduction of oil production and we do see as a result of that, there is an increased pressure on the economy."