India is likely to intensify diplomatic efforts with Angola to secure clearance for ONGC Videsh Ltd's acquisition of 50 per cent interest in an oil field in the oil-rich African country.

In April, OVL had cut a deal with Royal/Dutch Shell to buy its 50 per cent stake in the offshore Block 18 for $623 million but Angolan state oil company Sonangol blocked the move by exercising its pre-emption right.

The handover of Shell's stake to OVL cannot get through unless other partners in the production sharing contract and joint operating agreement -- British Petroleum and Sonangol -- give up their right of first refusal in favour of OVL.

BP has already given its waiver but a go-ahead has not yet come from Sonangol.

"There are reports that a state-run Chinese oil player has also thrown its hat in the ring for the coveted asset. New Delhi is intensifying diplomatic efforts to secure the deal," sources said.

Petroleum Minister Mani Shankar Aiyar, who till recently was planning a trip to Angola, may talk to Angolan President to block rumoured efforts by China to muscle in on the deal.

Sonangol had earlier told OVL delegation as well as Shell of its intention to pre-empt and later sell the assets with a view to achieve a better price.

"Aiyar's intervention should hopefully end the stalemate and lead to a favourable decision by the Angolan government to conclude the transaction," sources said.