"From then onwards, they will keep coming to Pakistan for the next five years and we will reciprocate by playing in the USA".
The Caribbean team will play the matches in Pakistan and the USA.
He added: "There were talks that the series should be played in November, but the weather conditions were not good, so we didn't take any risk".
Windies are set to play a three-match Twenty20 series in Pakistan in March and April next year, it was announced on Saturday.
"The series in the U.S. will be a triangular series with Pakistan, West Indies and a third team to be finalised every year".
Elaborating on the issue, Sethi revealed that both the national cricket boards signed an agreement to hold a series of T20Is, each year, for the next five years, in Pakistan and the US.
The West Indies was due to visit Pakistan this month, but Sethi said heavy smog in Lahore made organization hard.
He also made it clear that this bilateral arrangement between the two boards was outside of the official future tours program of the International Cricket Council (ICC).
West Indies are confirmed to play a three-match T20I series in Lahore in March next year, Pakistan Cricket Board chairman Najam Sethi announced at a press conference on Saturday (November 11).
A third team will also be invited to U.S. for a tri-series, said Sethi.
Pakistan Cricket Board, on the other hand is managing Pakistan Super League (PSL) 2018 draft in coming days where some 501 worldwide players are up for picks by owners of six teams. Following World XI's tour of the country, Pakistan also hosted Sri Lanka for a single T20I game which was played at Lahore.