Suncor Energy Inc, Canada's biggest oil company, said on Friday it is budgeting C$5.5 billion ($5.23 billion) for capital spending in 2010 and will restart construction on its Firebag Stage 3 oil sands project.

Suncor, which dominates Canada's oil sands region following its C$22.7 billion acquisition of Petro-Canada in August, will use C$1.5 billion for growth project funding at its oil sands operations and C$4 billion in sustaining existing operations.

The company said it will ramp up construction of Firebag Stage 3, which was about half complete before being deferred in early 2009.

Suncor expects production to start in the second quarter of 2011, with volumes then beginning to ramp up toward design capacity of about 68,000 barrels per day of bitumen.

It also plans Firebag Stage 4 with similar capacity and expects bitumen production in the fourth quarter of 2012.

The company plans to complete the Millennium Naphtha Unit and expand the St Clair Ethanol Plant.

Both Suncor and Petro-Canada halted their major oil sands projects last year as the economic crisis caused commodity prices to plunge and made credit scarce and expensive.

The company said last week it plans to sell as much as C$4 billion in assets, including a third of its natural gas operations, smaller interests in some North Sea fields and its Trinidad and Tobago holdings.

Suncor shares closed at C$36.44 on Thursday on the Toronto Stock Exchange. The shares have risen 56 percent over the past 12 months. ($1=1.052 Canadian Dollar) (Reporting by Ajay Kamalakaran in Bangalore; Editing by Gopakumar Warrier)