The Scottish champions are hot favourites to dispose of Basle in the qualifying round, starting with a victory in the first leg when they host the Swiss side at Parkhead on Wednesday night.

The return tie - on Wednesday, August 28 - falls only three days before the European transfer window shuts down for four months.

That would require O'Neill to move fast in order to secure an addition to his squad for a Champions League campaign. But the Celtic boss last night hinted that the groundwork for a deal had already begun and would continue over the next fortnight.

With the guarantee of financial rewards in the lucrative tournament, Celtic would then be able to buy and add to a squad already boosted by David Fernandez, Ulrik Laursen and Magnus Hedman.

It's understood that the missing piece of O'Neill's jigsaw for the season is a speedy midfielder who can link with the Parkhead forwards.

'The time element would be a concern,' said O'Neill.

'It might be so tight that we don't know until the last minute of the second game if we are through.

'If we're lucky enough to get through, we only have a couple of days after that to make a transfer.

'But that would not stop me searching around and looking at the possibilities now, in case that situation occurs at the end of the month.'

O'Neill, meanwhile, said it was too early to say if French wing-back Didier Agathe would be fit to return against the Swiss after he missed yesterday's win at Pittodrie.

'We played very well and scored four goals but could have had a lot more,' the Celtic boss said.