The proposed takeover requires approval from regulators in the European Union, United States, Australia and South Africa and is currently facing a detailed second phase review from the European Commission.
Regulatory clearance from each different jurisdiction will allow BHP Billiton (bhp.ASX:Quote,News) to formally launch its 3.4-for-one all scrip takeover offer for Rio Tinto (rio.ASX:Quote,News).
"We expect that the various regulatory processes will be completed by the end of 2008, after which we should be in a position to send the offer documents to you,'' BHP Billiton chairman Don Argus said in a letter to Rio Tinto shareholders.
Earlier this month the US Department of Justice (DoJ) and the Federal Trade Commission granted early termination of the Hart-Scott-Rodino waiting period, which satisfies part of the US merger control precondition of the proposed takeover.
The Australian Competition and Consumer Commission (ACCC) last month started its review of the proposed takeover.
Mr Argus said a merged company would be "without comparison'' in the resources industry in terms of strategy, asset mix and quality, and would generate "substantial additional value for shareholders''.
BHP Billiton estimates that the combined outfit could realise $US3.7 billion worth of synergies through the sharing of infrastructure and services at neighbouring assets.
Shares in BHP Billiton gained 75 cents to $39.00 by 10.33am (AEST), while Rio Tinto put on $2.32 to $121.47.
BHP follows Rio with huge price hikes
