Ferguson cast doubt on whether Ferdinand would accept Roy Hodgson's call for the World Cup double-header against San Marino and Montenegro after expressing concern about disruption to the meticulous way the 34-year-old prepares for games.
However, after Ferdinand produced another controlled display, including setting up Wayne Rooney's winner in Saturday's 1-0 triumph over relegation-haunted Reading, Ferguson confirmed the defender would report for duty at St George's Park on Monday.
"Rio will be joining up," said Ferguson.
It is believed Hodgson has spoken to the United boss to offer assurances about how the player will be treated, which may include not using him in the San Marino game.
Tonight's evidence showed why England want him involved in Podgorica though, as Ferdinand sauntered upfield before slipping a pass to Rooney - whose 21st-minute effort deflected in off Alex Pearce.
"He broke into the midfield very well," said Ferguson.
"He has always been good at that. He doesn't do it as much as he used to of course but today [Saturday] it paid off for us."
Ferguson made eight changes on Saturday and handed Alex Buttner a rare start.
The changes did not affect United's winning momentum, even if their performance was, at times, disjointed.
"It has been a great season for us," said Ferguson.
"Most of the time we have been playing well and obviously today [Saturday] doesn't reflect the 15 points ahead we are, it is the previous six months."
Ferguson refuses to accept a 20th championship is already secure even if it will only take 13 points from nine games to be mathematically certain following Manchester City's defeat at Everton, and United are on course to break their own record for an 18-point title-winning margin.
"People can say what they like," he said.
"You don't get points or medals for being complacent and we won't be."
United are clearly concerned about the effect this international break could have on their season considering they travel to Sunderland on March 30 for a lunchtime kick-off, and Chelsea 48 hours later for their FA Cup quarter-final replay.
"We are making arrangements for some players to fly home by privately hired jet after their matches to make sure they get home as quickly and as smoothly as possible," said Ferguson.
"Tiredness is a great leveller but we'll do our utmost to make sure we field the freshest possible teams.
"Private planes are going to cost the club an awful lot of money but it is something we feel we have to do."
If it is only a matter of time before United are crowned champions, the same seems true of Reading's change in status from Premier League to Championship club.
The Royals are now seven points adrift of safety and without a manager, following Brian McDermott's dismissal at the beginning of the week.
"No-one was more surprised than me," said caretaker boss Eamonn Dolan.
"It is well documented that Brian is a good friend of mine but the decision was made and we move forward."
Reading did not create many chances. But they still left lamenting referee Lee Mason's refusal to award a spot-kick for Nemanja Vidic's clear push on Adrian Mariappa inside the area at the start of the second half.
"It was a clear penalty but I think the referee thought I was on work experience and 'perfect a little 1-0 loss for Reading' and would be fine," he said.
"I wouldn't have expected that from the referee but what can you do?"