UPDATE 1-Suncor execs to take top posts in Petro-Can deal

* Suncor, Petro-Canada name top execs for merged firm

* Top three posts filled with Suncor executives

CALGARY, Alberta, April 22 (Reuters) - Executives at Suncor Energy Inc (SU.TO) will assume the top roles in the company after it wraps up its planned C$18.4 billion ($15 billion) takeover of Petro-Canada (PCA.TO) in the country's biggest energy deal, the firms said on Wednesday.

Under Suncor Chief Executive Rick George, who will also lead the merged company, Suncor's Steve Williams will keep his title of chief operating officer and Bart Demosky, now vice-president of business services at Suncor, with be chief financial officer.

The companies had already said Petro-Canada Chief Executive Ron Brenneman will be vice-chairman of the new entity, which will become Canada's biggest energy player, with dominant positions in the oil sands and off the East Coast.

It will also have extensive natural gas, international and refining and marketing operations.

Among current Petro-Canada executives, oil sands boss Neil Camarta will be vice-president of natural gas, Boris Jackman will lead the refining and marketing business and CFO Harry Roberts will be vice-president of integration.

Peter Kallos will keep his role as vice-president, international and offshore.

The companies announced the deal in March, pledging to cut costs while weathering low oil and gas prices.