Manchester United have now officially been world club champions twice following a ruling by FIFA on Friday to recognize their 1999 Intercontinental Cup triumph.
The council of the sport's world governing body said it had officially recognised the winners of the Intercontinental Cup, which was staged between 1960 and 2004, as club world champions.
The competition was usually played between the winners of the European Cup and South America's Copa Libertadores but was dogged by violence, disagreements over the format and disinterest from European teams. Liverpool, for example, refused to play Argentina's Boca Juniors in 1977 and 1978.
British clubs had a very poor record in the competition, with Celtic, Manchester United, Nottingham Forest, Liverpool (twice) and Aston Villa all losing finals before United finally beat Brazil's Brazilian side Palmeiras in 1999.
United also won FIFA's revamped tournament, the Club World Cup, in 2008.
Real Madrid are the most successful club across the history of the two competitions, with a total of five victories. The reigning European champions won the Intercontinental Cup three times (1960, 1998, 2002), while they secured a second Club World Cup triumph last season, though only after Cristiano Ronaldo's hat trick sealed a 4-2 victory in extra time over Japan's Kashima Antlers.
AC Milan also saw three Intercontinental Cup titles added to their 2007 Club World Cup victory. Barcelona have won three Club World Cups -- more than any other side -- but never lifted the Intercontinental Cup.
Brazilian club Sao Paulo are South America's most successful clubs in the international competitions, with 2005's Club World Cup final win over Liverpool being added to the back-to-back Intercontinental Cup tournaments they won in 1992-93.
No club from outside Europe or South America has ever claimed either of football's world titles.
Three-time Intercontinental Cup winners: AC Milan (1969, 1989, 1990), Boca Juniors (1977, 2000, 2003), Nacional (1971, 1980, 1988), Penarol (1961, 1966, 1982), Real Madrid (1960, 1998, 2002)
Two times: Ajax (1972, 1995), Bayern Munich (1976, 2001), Independiente (1973, 1984), Inter Milan (1964, 1965), Juventus (1985, 1996), Porto (1987, 2004), Santos (1962, 1963), Sao Paulo (1992, 1993)
One time: Atletico Madrid (1974*), Borussia Dortmund (1997), Estudiantes (1968), Feyenoord (1970), Flamengo (1981), Gremio (1983), Manchester United (1999), Olimpia (1979), Racing (1967), Red Star Belgrade (1991), River Plate (1986), Velez Sarsfield (1994)
*European Cup runners-up, only participated after champions Bayern Munich declined to play