CELTIC today officially pulled the plug on their attempt to sign Gabriel Tamas.

Interest in Marko Basa also appears to be cooling, despite reports from France that the Le Mans player is on the verge of joining the Parkhead club.

With their two long-term targets falling off the radar, Celtic are now redoubling their efforts to secure another central defender, and sources within the club confirm they remain hopeful business can be concluded soon.

However, there can be denying that, after weeks of serious negotiations - which included Peter Lawwell flying to France to discuss their offer face to face - missing out Tamas has been a frustration and disappointment to chief executive and manager Gordon Strachan.

The £3.5million deal to bring in 24-year-old Romanian international Tamas had been revived over the past few days after initially stalling over personal terms.

The player flew back to Bucharest last night to hold urgent talks with his agent, Florin Manea. But, the news he received today was not good.

Parkhead sources have made it clear that money was not the reason they finally decided to walk away.

In keeping with their regular policy of having options for every signing target, at the same time as Celtic had been negotiating with Tamas, they had also been in pursuit of 25-year-old Serbian centre-back Basa.

Le Mans had originally demanded more than £6.5m for their man, but this price was bartered down to £4.5m.

However, the Basa back up plan no looker looks like a runner, and the player is left with the choice of reviving interest from Hamburg, PSG, Spartak Moscow and Fiorentina.

Another target, Barcelona midfielder Marc Crosas, is also still waiting to hear if he is going to land his £2m move to Celtic.

The 20-year-old is continuing to prepare in New York for Barca's game against Red Bulls on Thursday, but would be at Parkhead within a matter of hours if the deal finally gets the green light from the Spanish club.

Thomas Gravesen could be on his way back to Spain, freeing up valuable wages.

The Danish midfielder - in the final year of his lucrative contract with Celtic - is a reported target for relegated Real Zaragoza.