CANCUN, Mexico -- A long-promised cup competition between Liga MX and MLS clubs is on its way to becoming a reality in 2019, sources have told ESPN.

The tournament would involve four teams from MLS and four from Liga MX, sources confirmed to ESPN FC, while a Liga MX source told ESPN Mexico's Rene Tovar that the competition doesn't yet have a name and a format hasn't been locked in, but will take place in the second half of 2019.

The teams haven't been confirmed internally, but MLS sides from the West Coast are expected to be well-represented, as well as a Mexican club close to the border, a source told ESPN FC.

The two leagues previously formed the SuperLiga, which featured four teams each from both leagues and ran from 2007-2010. MLS commissioner Don Garber has previously stated that it was ahead of its time.

Liga MX and MLS announced a collaborative agreement in March last year, which included an annual Campeones Cup -- to be played annually between the champions of each league -- as well as a commitment to a future MLS All-Stars vs. Liga MX All-Stars game

In a statement to ESPN FC, MLS said: "We were very excited to kick off our unique and historic partnership between Major League Soccer and Liga MX in 2018, and a memorable first edition of Campeones Cup. We look forward to Atlanta United hosting the second edition this August 2019. It complements the rivalries between national teams and is a reflection of our shared values.

"As we stated when announcing the partnership, a competition featuring possible interleague play was under consideration. We continue to have discussions about a possible event."

The change in the CONCACAF Champions League format since 2017 allowed MLS and Liga MX clubs to enter the competition at the round-of-16 stage, leaving some room to maneuver. Liga MX teams also pulled out of the Copa Libertadores in 2017 due to the South American tournament's new scheduling, but creating a cup competition with MLS has proven challenging, largely due to calendar issues.

As early as 2014, Liga MX owners discussed adding MLS teams to Mexico's domestic cup competition, Copa MX, and MLS said then it was open to a proposal.

Liga MX president Enrique Bonilla stated back in November 2016 that the Mexican league was open to a cup competition, while MLS and both sides have stressed the need to work with each other to strengthen the region.