The plant is seen as crucial to avoid power shortages in Sri Lanka by 2017/2018.
Sri Lanka now has one 300MW coal plant supplied by China which is currency shut down for scheduled maintenance.
A second stage is expected to be connected to the grid at the end of the year.
Ranjith Gunewardene, additional secretary of Sri Lanka's power ministry said a power purchase agreement has been finalized and may be signed with a week.
The joint venture plant between Sri Lanka's Ceylon Electricity Board and India's National Thermal Power Corporation has been delayed due to disputes over the parameters that indicate the efficiency of the plant and maintenance fees.
Gunewardene said international tenders would be called to build the plant.
International turnkey contractors or equipment suppliers are usually required to guarantee a specific 'heat rate' or the amount of power generated from coal based on its calorific value.