By Felix Onuah

ABUJA, Nov 17 (Reuters) - Nigeria has reached a deal to pay $5.1 billion in unpaid bills to oil majors including Royal Dutch Shell (RDSa.L) and Exxon Mobil (XOM.N) , the minister of state for oil said on Thursday.

The Nigerian National Petroleum Corporation (NNPC), the OPEC member's state oil firm, has amassed a total of $6.8 billion in unpaid bills up to December 2015, so-called cash calls, that it was obliged to pay under joint ventures with Western oil firms, with which it explores for and produces oil.

Oil minister Emmanuel Ibe Kachikwu said the agreed amount, which is $1.7 billion less than the total amount owed, would be paid within five years, interest free.

Under the arrangement, payment will be in the form of crude oil cargoes but only when Nigeria's production exceeds 2.2 million barrels per day, Kachikwu said, which is the nation's current production when all fields are operating properly.

"If for any reason we did not meet (the) threshold we will not pay the $5.1 (billion), so that is fantastic," he said of the deal, which has been approved by the National Economic Council, an advisory body to the government.

Kachikwu last week said Royal Dutch Shell, Exxon Mobil, Italy's ENI, Chevron and France's Total had "accepted" what he described at the time as an "outline settlement".

All five of the oil majors declined to comment when approached by Reuters.

The petroleum ministry has for more than a year been trying to reduce its financial obligations, which have accumulated over several years. Kachikwu said there is at least $2.5 billion in additional debt that has accrued this year that it is still working to repay.