The West Indies will be forced to battle the likes of Afghanistan, Ireland, the Netherlands and Papua New Guinea to secure qualification for the 2019 ICC World Cup.
It comes after their seven-wicket loss to England at Old Trafford on Tuesday.
Only a 5-0 series win or 4-0 with a tie or no-result against England would have seen West Indies pip Sri Lanka before the cut-off point.
But having failed to qualify for the elite Champions Trophy tournament in Britain earlier this year, the Windies suffered a 13th defeat in their last 14 completed ODIs against England.
The Windies batting first were restricted to 204 for 9 in the contest that was reduced to 42 overs per team due to a wet outfield.
Skipper Jason Holder 41 not out and Chris Gayle 37 were the top-scorers against Ben Stokes 3 for 43.
England in response raced to 210 for 3 in 30.5 overs with Jonny Bairstow unbeaten on 100 from 97 balls.
With September 30 set as the cut-off date for automatic qualification, the Windies who are on 78 points, cannot move ahead of Sri Lanka (86) in the ODI team rankings regardless of other results in the remainder of their five-match series in England.
As a result, 1996 World Cup winners Sri Lanka have become the eighth and last team to qualify directly, joining Australia, Bangladesh, England, India, New Zealand, Pakistan and South Africa.
West Indies, who won the first two World Cups, could still take part in the main 10-team tournament if they are one of the top two sides in next year’s qualifying competition.
That event, which is yet to have a confirmed venue, will see the Jason Holder led team joined by the bottom three sides in the ODI rankings – Afghanistan, Zimbabwe and Ireland – as well as the top four sides from the ICC World Cricket League and the top two from the WCL’s Second Division.
The Netherlands, Papua New Guinea, Scotland and Hong Kong presently occupy the top-four spots on the WCL standings with two games to play.
The next World Cup, the fifth to be staged in Britain, will take place from May 30 to July 15.