The newly crowned Premier League champions have caused an uproar by slating their visit to the continent to coincide with the running of the quadrennial Asian Cup, which will be co-hosted by Malaysia, Indonesia, Vietnam and Thailand.

Asian Football Confederation president Mohamed bin Hammam launched a scathing attack on the English champions on Monday, and Blatter has backed demands for United to reconsider.

"The Asian Cup is on a date reserved for competitions for the confederations, and they should also be respected by clubs who are touring in the same region where these competitions are taking place," the FIFA president said. "I would personally appeal to the club, to the associations, but also to the organizers in the different countries. We have an opportunity for solidarity for football."

Malaysia is the last stop on United's jaunt on July 27, with the tour kicking off in Tokyo on July 17 followed by a stop in Seoul three days later and a match in Macau on July 20.

Those dates clash with the latter stages of the continental championship, which will feature all four co-hosts as well as defending champions Japan and nations such as China, South Korea and Iran among the 16 participants and runs from July 7-29.

As a result, the tour was not ratified by the AFC during their Congress in Kuala Lumpur in Tuesday.

The FIFA president has already been in contact with Football Association chairman Geoff Thompson and he hoped the Old Trafford club would reconsider.

"I had an opportunity to speak with him the other day when we met in Nyon and he said I will work on that but that it's not so easy because this was an invitation by the government (of Malaysia), not the federation," Blatter said.

"But we have a structure in FIFA, and I told the sports minister here in Kuala Lumpur (Monday) that when you organize a tour you have to go through the national association," Blatter said. "They have to ratify such a match. They have to inform the confederation.

"For the clubs, FIFA's OK is not necessary, but I'm sure if such a case will be presented to the club, Manchester United, that the organizers of the tour will understand such a situation."

The match was to form part of the country's celebrations of 50 years of Malaysian nationhood but Tengku Abdullah Sultan Ahmad Shah, the president of the Football Association of Malaysia, conceded the game may not now go ahead.

"We have to abide by the ruling, I guess," he said. "That's the order of the day and we have to abide by that. If they want to come at that time they can't come. Now the sanction has not been given so we have to follow the ruling. They can't come during the Asian Cup, they have to rearrange.

"By the look of it, the Asian Cup will have to take precedent. This is bad news for the fans but this is the feeling of the family of Asia."