By Oludare Mayowa and Chijioke Ohuocha

LAGOS (Reuters) - Nigeria plans to issue a $500 million debut Eurobond on Friday after a roadshow in the United States and Europe, the head of the country's Debt Management Office (DMO) told Reuters on Monday.

Sub-Saharan Africa's second-biggest economy will begin a roadshow in the United States and Europe on Tuesday for the planned bond, which has been repeatedly delayed.

"The bond issue will be concluded on Friday January 21. A new window is being opened, particularly for the private sector to have ,  access to the international capital market," DMO Director General Abraham Nwankwo said by telephone.

IFR, a Thomson Reuters news service, said the roadshow would begin simultaneously on the U.S. West Coast and in Germany before continuing in New York and London on Wednesday and concluding in Boston the following day.

"The finance minister left yesterday for it, and the head of Debt Management Office and some other officials have all gone for it too," a senior finance ministry official said, giving no further details and asking not to be named.

Africa's top crude oil exporter first announced plans to borrow in the international bond market in September 2008 but has put the issue on hold several times, most recently in December, citing adverse market conditions.

Finance Minister Olusegun Aganga told a news conference just over a week ago that roadshows were planned in the United States and Europe and that the issue would be going ahead "in the next two to three weeks".

The aim of the 10-year bond is to set a benchmark in the global market for Nigeria rather than to raise funds, meaning the pricing is considered more important than the timing.

Nigeria last year appointed Deutsche Bank and Citigroup as bookrunners for the Eurobond and named Barclays Capital and FBN Capital, a subsidiary of Nigeria's First Bank, as its financial advisers.