At the same time, nationalist residents on the controversial Garvarghy Road route through Portadown announced plans to hold nightly pickets on the roadside from today.
Mr Ahern, who yesterday held a brief meeting in Belfast with Mo Mowlam, the Secretary of State for Northern Ireland, indicated that his support for any decision by her on the fate of Sunday's planned march was not guaranteed.
"Nobody wants to see the march forced through," he said. Asked if he would support her decision - due later this week - he added: "That will depend on what it is."
A more trenchant view still came from the Irish Foreign Minister, Ray Burke, who said it would be "folly" to force the parade through.
Their remarks were seen as a reminder of just how much hangs on Ms Mowlam's decision.
By allowing the march through, she risks alienating the Irish Government and the Nationalist community at a critical time for the prospects of peace.
Against that, The Independent revealed last week that sections of the Orange Order have drawn up plans to bring the province to a standstill if the Portadown march is not allowed through its traditional route.
One theory is that the Government might allow the march to go through, ensuring a short, if sharp backlash, rather than a long, drawn-out stand- off.
Mr Ahern, who will be raising the issue in talks with Tony Blair in London tomorrow, went out of his way to praise Ms Mowlam as a person of "commitment, energy and drive".
He also said he would do everything possible to bring about peace in Northern Ireland.
"I will play my part and I look forward to doing that maybe in a more helpful way than has been done in the past," said Mr Ahern, who later held talks in Dublin with representatives of the Portadown residents and others from the Ormeau Road in Belfast.
Earlier, Ms Mowlam said she was surprised by the decision of the Nationalist residents to hold the roadside vigils.
"I hope the demonstration is peaceful and within the law and in the end that it will still work for common sense to prevail," she said.
Brendan McKenna, spokesman for the residents, said a street festival planned for the day of the parade on Sunday will also go ahead.
He urged the Secretary of State and the RUC Chief Constable to re-route the Orange Parade from Drumcree Church.
"For one year the Nationalist community must have a breathing space from the parade, from the fear, the anger and the real apprehension it causes."
He also confirmed elaborate plans for a "justice camp" and protests involving women and children.
The protests were immediately condemned by unionists as deliberately provocative. The Democratic Unionist Party's Nigel Dodds said: "It's a clear attempt to up the ante. This is deeply regrettable."