Sir Alex Ferguson is confident of signing Wilfried Zaha for £12m from Crystal Palace by the end of the week, with the aim of loaning the winger back to the Championship club for the remainder of the season.

The Manchester United manager did not travel with his squad to Qatar for the four days of warm-weather training that they are enjoying before Saturday's FA Cup fourth-round tie at home to Fulham. Instead he remained in England to finalise the deal for Zaha, who has emerged as one of the most exciting talents outside the Premier League. It is unclear when Ferguson will join his players in Doha, the Qatari capital.

Arsenal have also been keen to sign Zaha, who made his debut for England in the friendly against Sweden in November, and their manager, Arsène Wenger, said last week that he was "looking at him but, at the moment, we have not made any bid". David Gill, the United chief executive, had already admitted United's interest for the first time.

The 19-times champions appear to have won the race to sign Zaha even though Palace's stance has been that the 20-year-old is not for sale, as he is important to their promotion push. But United's willingness to loan him back to Selhurst Park for the season's final months has helped smooth the way towards an agreement.

Palace may also request that, in addition, at least two more United players – Nick Powell, the 18-year-old midfielder, may be one – also join on a temporary basis until the close of the campaign to help with their attempt to reach the Premier League. This, though, is not thought to be pivotal to any prospective deal. Ian Holloway's side are fourth in the Championship, two points away from an automatic promotion place.

The Football Association has written to Ferguson to ask for an explanation of his comments regarding the assistant referee Simon Beck after United's 1-1 draw at Tottenham Hotspur on Sunday. Ferguson has until 6pm on Thursday to respond.

Ferguson was unhappy with Beck, particularly over the official's failure to flag for what United felt should have been a penalty for a foul on Wayne Rooney by Steven Caulker. The manager said: "The stand-side linesman didn't give us a thing all day. For me it was a poor performance by him. Why he never saw the penalty kick from Wayne Rooney and some other decisions … We remember him well from his time at the Chelsea game [in April 2010] when [Didier] Drogba was three yards offside and he gave onside. He had a shocking game. I'm disappointed in his performance, I really am. He had a bad game and we never got anything on that side of the pitch."

Whether Ferguson faces a charge will depend on whether he is viewed as having questioned the integrity of Beck, as there is no issue with opinions offered by a manager. If charged with misconduct and found guilty United's manager could face a fine or touchline ban.

Fulham have complained to the FA about United offering a £5 discount on tickets sold to members for Saturday's FA Cup tie at Old Trafford. The FA has written to United for an explanation and asked the club to suspend ticket sales until the matter is resolved.

According to FA rules, each club is due 45% of all ticket sales for a match at this stage of the competition. Fulham wrote in a tweet on their official feed: "Fulham Football Club has contacted the FA to complain about Man United discounting FA Cup match tickets for their fans."

The clubs had agreed a price for all tickets – as is the practice for FA Cup games – and decided on £45. But United have since offered a discount to members; although FA regulations allow clubs to offer a discount, Fulham's stance is that this must be agreed with the opponents for the respective match. The club were not asked and would not have given permission because they do not want their fans to have to pay more than some home supporters.

However, it is understood that since United offered a similar discount for last week's third-round replay with West Ham and also do so for Capital One Cup games, they are comfortable with repeating the procedure for Fulham's visit.