(Reuters) - Halliburton Co (>> Halliburton Company) will buy Baker Hughes Inc (>> Baker Hughes Incorporated) for about $35 billion (22 billion pounds) in cash and stock, creating an oilfield services behemoth to take on market leader Schlumberger NV SLB.N as falling oil prices threaten to erode demand.

The combination, which will likely raise antitrust concerns, could help the companies better cope with weak oil prices. Global crude oil prices have slipped from over $100 a barrel in June to less than $80 on excess supply and tepid demand growth.

Despite the market share boost that a tie-up of the No. 2 and No. 3 oilfield companies may bring, the combined entity would only have about half the market capitalization of sector leader Schlumberger NV (>> Schlumberger Limited.), which is valued at $122.6 billion.

(Reporting by Swetha Gopinath, Shubhankar Chakravorty and Manya Venkatesh in Bangalore; Editing by Lisa Von Ahn)