LONDON  - Andrew Strauss, the former England captain, has warned that the return of Kevin Pietersen to the squad could cause "problems" if the issues that led to Pietersen being dropped have not been fully resolved.Pietersen was left out for the third Test against South Africa in August after sending messages about Strauss - who retired from cricket in the wake of England's series defeat - to members of the opposition. Pietersen had previously quit limited-overs internationals amid complaints about his schedule, although he has now reversed that decision. A parody Twitter account that Pietersen believed was being encouraged by some of his team-mates also caused a problem within the dressing room.However, after being left out of England's squads for the World Twenty20 and the Test tour of India, Pietersen was given a route back into the side after agreeing a process of "reintegration" with the ECB and signing a four-month central contract. He was subsequently added to the touring party for India and Strauss believes it is in the team's best interests to mend the relationship with Pietersen."It will be difficult," Strauss said in an interview with the Guardian newspaper. "One of the problems is that there are two separate sections. One is going on in meeting rooms between KP and the players and on the other side is this media intrigue. From Andy Flower's point of view, they need to get that first part right. If everyone is happy in the dressing room they will play well. But if it's not resolved then it is a problem. I honestly think it's a real problem."If they can make it work, then obviously England will be a better side with KP in it because he's an outstanding player. But if, behind the scenes, things are difficult and resentment is harboured and, if KP is not fully committed to England, there are going to be problems. But it's in everyone's interests to make it work."Strauss again denied that the Pietersen saga hastened his retirement but said he felt guilty leaving the issue for Flower, England's team director, and Alastair Cook, his successor as captain, to sort out. He added, though, that his decision to step away may have helped speed up the process of reconciliation."Maybe it actually makes it easier for the team that I'm not there because some of it was directed to me. It would have been harder if I'd stayed," he said. "I think that it can be [healed]. But everyone has to desperately want it to happen and they all need to let bygones be bygones and not have any grudges and bitterness. Everyone has to want to move forward for the right reasons. That's the question mark and so it's hard for me to tell. But it saddens me that we've been through this - after all the hard work we put in as a group for three-and-a-half years. We all genuinely believed in this special bond and chemistry we had. Unfortunately we've slipped from there and the guys are going to need to recover that. It's going to be tough."Strauss also revealed that Pietersen was not among the England players to receive a personal letter informing them of his decision to retire. The letters were delivered individually to members of the squad playing an ODI against South Africa in Southampton during the time that Pietersen was not being considered for selection. Instead, Strauss delivered the news by text, admitting that it "was a strange time for the two of us. A lot had happened and during that period we were quite estranged from each other."They have now put the episode behind them, with Strauss admitting things could have been handled better on both sides, although he stopped short of condoning Pietersen's actions. "Kevin has since come up to me and apologised for it and I respect that," he said. "He seemed contrite and I think he was sincere. Looking back I think it was wrong some of our players were following that Twitter account. But I still don't think it's a justification for what Kevin did."