Singapore Exchange is likely to offer as much as A$48 per share to take over ASX Ltd, valuing the Australian bourse operator at A$8.4 billion ($8.3 billion), according to a source with knowledge of the deal.

The source said around 43 percent of the offer, to be formally made on Monday, will be in cash with the rest in SGX shares.

"There is a price range being finalised. A$48 is the top of the range," said the source.

At that level, the offer reflects a 37 percent premium over ASX's last traded price of A$34.96 before shares of both companies were suspended on Friday.

An SGX spokeswoman was not available for comment, but the bourse operator said late on Sunday it will make an announcement on Monday.

ASX was not immediately available for comment.

Both the Singapore Exchange and the ASX are under pressure to expand and find new business opportunities and counter the threat of alternative trading systems. ASX has also been looking at new business opportunities ahead of the end of its monopoly in 2011.