A corresponding rule change will allow them to trade those slots, enabling a club to field an entire roster of non-Americans.

The rules announced today will allow Chivas USA to mimic its Mexican namesake in Guadalajara, which boasts never having fielded a non-Mexican. It also could result in an MLS team appearing like London club Arsenal, which can generate an entire starting side without a native Englishman.

Foreigners without nonresident alien status will be limited to 112 of the 392 players in the league, or just under 30 percent.

MLS deputy commissioner Ivan Gazidis said it was unlikely any team would employ an entirely non-American roster, but said the changes were made for flexibility and to accommodate the addition of the San Jose Earthquakes expansion team next season.

"We believe we need to dip into the international market in the short term," said Gazidis, who added that MLS's recently created youth development program will provide players in the medium-to-long term. "Americans are and will be the backbone of league. But I don't think I'm saying anything controversial when I say we don't believe the domestic talent pool is limitless."

"Every expansion is going to dilute talent, and that's not desirable for anybody."

Besides the Earthquakes, Seattle will join MLS in 2009, with another team possibly in Philadelphia or St. Louis that would bring the league to 16 teams.

Clubs had been limited to four "senior internationals" and three "youth internationals" — non-Americans under the age of 25. The league is abolishing the distinction between the two and increasing the number to eight on the 28-man rosters — with the option to trade for more.

The league's board of governors decided to increase their foreign-player limits just before the MLS Cup championship on Nov. 18 in Washington.

It also agreed to not count for at least two more years three players whose salary exceeded the $400,000 individual maximum under the "designated players rule" — an exemption that allowed teams to acquire a player outside the approximate $2.2 million salary cap.

The designated player rule adopted last year allowed teams to acquire high-profile foreigners such as David Beckham by the Los Angeles Galaxy and Cuauhtemoc Blanco by the Chicago Fire. Each team was granted one designated player allocation, but could have traded for a second.