Barclays has formally launched its 65 billion (£43.6 billion) bid for Dutch bank ABN Amro.
The high street lender is hoping to beat a 71 billion (£48 billion) rival offer by a consortium which includes the Royal Bank of Scotland (RBS).
ABN's board withdrew its support for a Barclays takeover last month, saying that it wanted to ensure "a level playing field" for the competing bids.
In a statement today Barclays confirmed that its proposed cash and share offer for ABN will begin tomorrow and run until October 4th.
The British bank is offering ABN investors 2.13 new Barclays shares and 13.15 (£8.90) for each of their shares.
"Further to the announcement of July 23rd 2007, setting out the revised terms of Barclays' offer for the shares of ABN Amro Holding, Barclays announces that it has received the regulatory clearances required to publish its offer documentation and is formally launching its offer for ABN Amro, which will open for acceptance tomorrow," the group said.
The launch of Barclay's formal offer for ABN comes as the shareholders of one of the companies involved in the rival RBS bid prepare to vote on whether to back the second takeover approach.
Investors at Belgian-Dutch bank Fortis will decide later today whether to back the offer for ABN proposed by the company's board.
They will also decide whether Fortis should issue 13 billion (£8.79 billion) in shares to fund the bank's part of the consortium deal, which along with RBS also includes Spain's Santander.
Meanwhile ABN has announced that it intends to hold an extraordinary meeting of its shareholders on September 20th to discuss the rival offers put forward by Barclays and the RBS consortium, with the Dutch group facing the biggest bank takeover ever made.