Iranian President Mahmoud Ahmadinejad is heading to Africa on a three-nation tour that includes a visit to uranium-rich Niger in a bid to boost economic and political relations.

Reeling under crippling economic sanctions orchestrated by the US, Iran has been trying to improve its ties with several countries that are outside the American orbit.

Ahead of the trip, Ahmadinejad told reporters that the expansion of ties with African countries is among "absolute, irrevocable and principle policies of Iran".

"Also, we will try to consolidate ties and take more giant strides for all-out expansion of relations," said Ahmadinejad.

The Iranian leader will visit Benin, Niger and Ghana on the first leg of his tour. He will meet the leaders of all three countries to sign agreements on expanding political and economic relations. Talks on the energy policies of Iran and African nations are expected to dominate the agenda.

Underscoring the importance of promoting independent states in Africa, he used the opportunity to criticise former colonial powers, which he accused of "bullying".

"He will lead a large delegation and both our nations will discuss cooperation and means of strengthening it," said Iran's ambassador, Mohammed Nikkah, following a meeting with Niger's President Mahamadou Issoufou. Nikkah added that the visit will provide "excellent opportunities that will benefit both peoples".

Niger is the world's fourth largest producer of uranium, which Iran is looking to buy for its contentious nuclear programme. Niger's relations with its former colonial power, France, have been damaged by uranium deals.

Iranian officials said Ahmadinejad's visit was finalised following invitations extended by African leaders.

Ahmadinejad, who has previously visited 11 African nations, had signed bilateral agreements with many of them.

Tehran has also been improving relations with a number of other countries including Latin American nations, Pakistan, India, and Egypt in order to beat the sanctions which have hit Iran's oil trade, the lifeline of the country's economy.