Director General of Debt Management Office (DMO), Abraham Nwankwo, on Thursday identified four infrastructure areas that Nigeria must invest over $100 billion in to get the economy functioning again.

These, according to him, are power ($18-20 billion), rail tracks ($8-17 billion), roads ($14 billion) and oil and gas ($60 billion).

Nwankwo spoke in a paper entitled, "Prospects for the Nigeria Infrastructure Fund," at the Nigeria Infrastructure Summit in Abuja.

"These infrastructure and related investments are critical to achieving 13 per cent annual growth rate of GDP set by the government and to make Nigeria one of the 20 largest economies in the world by 2020," he stated.

He noted that adequate infrastructure is an engine for economic growth and development, noting that there is huge infrastructure deficit in critical sectors.

According to him, on power, only 40 per cent of Nigerians have access to electricity and that Nigeria currently requires more than 10,000mw.

The DMO boss pointed out that installed generation capacity is currently 6,000 MW, but available energy output is only about 3,000mw compared to 39,000mw in South Africa, with a population less than one-third of Nigeria's.

Port service was very inefficient and the facilities were in deplorable state until it was recently concessioned, he added.

Nwankwo maintained that Nigeria's railway infrastructure is in dilapidated state and in any case has a very limited coverage.

"Locomotive availability of 6 per cent in Nigeria is dismal in comparison with 75 per cent for Africa. The railways contribute only 1per cent to national transportation," he said.

On National Independent Power Projects (NIPPs), Nwankwo stressed that expected additional generation capacity totaling 4,777mw: Sapele (561mw), Alaoji (961mw), Ihovbor (451mw), Egbema (338mw), Gbarain (225MW), Omoku (225mw), Calabar (561mw), Omotosho (451mw), Geregu (434mw), Oloronshogu (680mw, is in the offing.