Dentons has filed a claim against the Republic of Guinea and two of the country's ministries for $10.2m (£6.1m) the firm says it is owed in unpaid fees.

The fees relate to Dentons' advisory work on the development of a $20bn (£11.9bn) mining and infrastructure project in Simandou, in the southeast of the country.

In its lawsuit, filed in a District of Columbia court, Dentons alleges the Republic and its geology and mining ministries "have repeatedly acknowledged" they owe the law firm the fees, which cover more than 10,000 hours of work carried out between May 2012 and June 2013.

This work included producing "scores of reports, presentations, memoranda, drafts, negotiator notes and other deliverables including briefings to the Ministry of Mines, the Ministry of Finance…and a working group designated by the President of Guinea", and that the Republic "repeatedly asked the firm to continue with [this] work".

Dentons' work with the Republic has been headed by Washington DC energy partner Jonathan Cahn, who also supervised subcontractors including investment banking firm Lazard and engineering firm Khatib & Alami for the Simandou project.

On 1 April 2013, the Republic made a partial payment of $2m to Dentons, on the order of President Alpha Conde.

In August 2013, Cahn and a Dentons team travelled to the Guinean capital Conakry for a meeting at which the country's minister for mining Mohamed Lamine Fofana said the firm would be reimbursed for its services in full.

At the meeting, Dentons says the Republic acknowledged it owed the fees, but had not budgeted for the owed amounts.

The then finance minister suggested the payments would be made from relevant funds provided to the Republic by the World Bank, and that the Government would pick up the tab if the invoices could not be covered in full.

Dentons says neither the World Bank nor Guinea has since paid these fees.

A firm spokesperson told Legal Week: "We regret the need to resort to litigation to ensure we are paid for the value we provided to the Republic of Guinea and its people on this important project.

"We do not think it is appropriate to comment further on pending litigation, whether on this action or other actions that have been filed, other than to say we hope this matter is swiftly resolved."

One of the poorest countries in the world, Guinea was in 2012 ranked 176th of out 187 countries on the UN Human Development Index, with 2011 World Bank data putting GNI (gross national income) per capita at $600.