CELTIC have sent a warning letter to Benfica ordering them to stay away from Fraser Forster.

Neil Lennon sought to reassure club's supporters last night that neither the goalkeeper nor any other player will be allowed to leave before the transfer window closes on Monday.

Forster created uncertainty by being vague about his future in the aftermath of Celtic's qualification for the Champions League. Although he is only one year into a four- year contract, the 25-year-old has pre­viously hinted about moving for the sake of his international career and Benfica have persistently made approaches which have not been appreciated at Parkhead. On the eve of Celtic being drawn against Barcelona, AC Milan and Ajax in the Champions League Forster had said: "I am obviously a Celtic player at the minute and we will have to see what happens over the next few days."

Lennon was unequivocal about the goalkeeper, who has been drafted into the England squad for their upcoming World Cup double-header against Moldova and Ukraine, saying "he's not for sale". When asked if he felt Forster's focus was solely with Celtic, Lennon responded: "I think it will be once the window shuts. He's got a lot to look forward to but he's not for sale. We had no confirmed bids for him. We have actually written a letter to one club, just warning them off basically."

Celtic may currently operate at an entirely different level from all other clubs in Scotland but, like the rest, they are susceptible to the vagaries of this weekend's transfer closing over a staggered, 49-hour period. The Scottish Football Association decided that the window for registering new players should close at 11pm tonight, whereas in the majority of other European countries - including England, Germany, Netherlands, Italy and France - signings remain possible until midnight on Monday. Theoretically any SPFL club could sell a player if an acceptable bid is received on Sunday or Monday, and then be unable to replace him. Uefa had requested a standardised closure of the window on Monday but the SFA exercised its right to apply an earlier deadline.

"I don't know why but it doesn't make it any easier," said Lennon. "I'll be glad when it closes because there it is, there's your squad to work with: no-one's leaving, no-one's coming in and we can get on with it. It drives you crackers sometimes. You sometimes go boom, boom, boom, boom, boom and make four or five deals in one day and that is really not what you want. In the old days you could say 'well, I could do with a player come December and we'll bring this one in' to replace an injured player. That was a lot easier for managers. But we know what the stipulations are and try to work within them as best we can."

Celtic presented Nir Biton as their fifth summer signing yesterday - Teemu Pukki will become the sixth pending the successful completion of a medical - and Lennon said the 21-year-old Israeli will be in the squad as soon as he has proved his fitness. Celtic face Dundee United at 12.45pm today. "He's a class player; he's tall, he's got a good engine, he's got soft feet, he's got a good range of passing, and he's powerful when he gets going. What he will bring is a bit of extra quality to the midfield because we have been a little bit light there since Victor [Wanyama] left."

Biton becomes Celtic's second Israeli central midfielder but Lennon said there no implications for Biram Kayal. "Biton can do both, he can be a box-to-box one as well. I've seen him play both positions: more as an attacking midfielder for his club and for his country, and I've also seen him play in a defensive role. We have liked him for over a year now."