The star has given his former bandmate - who quit in 1995 before returning in 2010 - until January to decide whether he wants to reunite with the rest of the group for 2014.
Speaking to The Sun newspaper, he said: ''I'm hoping for five, that would be the best and then a big, big tour.
''We're brothers. When we're back together in a room, it's the same as it's always been.
''We will all see each other in January and find out for certain then.''
The 'Let Me Go' hitmaker also refused to be pitted against his friend, despite releasing his album 'Since I Saw You Last' only a week after Robbie's record 'Swings Both Ways' came out.
He insisted: ''I never challenge him, he's far bigger than me. We did that nearly 20 years ago but it's changed.
''We are great friends now, I've got a song on his record and he has one on mine.''
After joining 'The X Factor' UK as a judge in 2011, Gary will step aside to focus on his music and he admitted he looks up to ageing iconic rockers The Rolling Stones when it comes to achieving similar longevity.
He explained: ''What makes a band like that still go on stage is that they must be having fun. That's the way we have it and I want t keep on going and going.''