Barclays said tonight it expects to publish its offer document for its planned €64 billion takeover of Dutch rival ABN Amro in about six weeks.

Barclays said it and ABN were making “excellent progress” with the key regulatory filings needed for the offer. It said it expects to complete most of the relevant filings by the end of the month. It was confident there would be no substantive anti-trust issues to address for the deal.

It said one of the key approvals would be that from US authorities clearing the controversial agreement for ABN Amro to sell its US LaSalle bank to Bank of America.

Meanwhile a key member of the rival Royal Bank of Scotland consortium circling ABN Amro said it would run right up against a formal deadline before updating investors on its bid plans, suggesting that a host of potential obstacles still stands in the way of its offer for the Dutch bank.

Maurice Lippens, the chairman of Fortis, told investors at the Belgo-Dutch bank's annual meeting that the consortium was "still deliberating our position" and would clarify its position on Sunday, the final date imposed by the Dutch regulator for an update.

This flies in the face of earlier reports that the consortium would tell investors of its latest thinking before the AMF deadline. The Spanish bank Santander is the third consortium member.

"On Sunday the banks and the consortium will clarify their position," Mr Lippens told the annual meeting. He said the consortium could publish a formal offer, present a bid timetable or even walk way from the bid battlefield.

ABN's management, led by chief executive Rijkman Groenink, have rejected the consortium's €72 billion (£49 billion) advances in favour of the prevously agreed €65 billion deal with Barclays and an accompanying legally contentious sale of its American arm LaSalle to Bank of America.

Today's comments by Mr Lippens suggest that the consortium, which wants to buy LaSalle as well as the rest of ABN, is keen to exhaust all alternatives. It has been holding talks with Bank of America in an effort to head off damaging legal action in the event of it disrupting the $21 billion (£10.5 billion) agreed LaSalle deal.

The RBS bid is two-thirds cash and one-third shares in the Edinburgh-based bank. ABN has consistently raised questions over the funding of a bid. Between them, the trio will raise fresh debt and equity, underwritten by Merrill Lynch. Asset disposals may also follow.

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