MLS commissioner Don Garber announced the changes to the post-season format and explained a new system in which the play-offs will be open to two additional clubs in 2011.

Garber also confirmed that the league is beginning to investigate moving to an international calendar, which would align MLS with most European leagues' calendar.

He said: "The bottom line is we're telling the world we're going to begin taking a very serious look at this whole issue and what kinds of things we need to do to determine if it makes sense for us."

The immediate changes will take place next October, with the MLS Cup play-offs featuring an additional round for the bottom four qualifiers in a 10-team system.

Garber said those teams would meet in a knockout format for the right to qualify for the eight-team main field in the play-off bracket.

It has yet to be decided whether the fourth and fifth placed teams in each conference will play each other, or whether it will be the teams ranked seventh through to 10th in an overall standings format - but a decision will be made in 30 days.

Garber also confirmed that the 2011 season would consist of a 34-game schedule in which each of the league's 18 teams - including newcomers Portland and Vancouver - play each other home and away.

That season may kick off a week earlier in March.