He made the remarks in his address to Conference on 'West Asia' in New Delhi.
He said that Indian private sector is interested in investment in Chabahar, but, Indian government lacks necessary resolve.
Agreement worth 75 million dollars on investment in Chabahar development plan was signed in April 2015, by Indian Minister of Shipping, Road Transport and Highways Nitin Gadkari and Iranian Minister of Roads and Urban Development Abbas Akhundi.
The ambassador complained that Indian government is pursuing cautious diplomacy after cancellation of sanctions.
He said that India should fulfill commitment to the agreements with Iran.
Ansari asked whether India wants to lose the excellent opportunity by the delay.
He said that India has very important interests in western Asia and should move for achieving them.
Referring to Iran's role in establishment of peace and stability in the region, the ambassador said that Iran is involved in campaign against the extremist groups threatening security in the region.
The 2-day conference dubbed 'West Asia Conference' kicked off on Thursday.