Trade ministers from the 12 countries involved in a Pacific Rim free trade deal are unlikely to meet again by the end of this month amid remaining differences that prevented them from finalizing negotiations last week, sources said Thursday.

Japan, the United States and the 10 other countries negotiating the Trans-Pacific Partnership will look at possibly reconvening a ministerial meeting in September, but the outlook is uncertain due to political schedules in some of the member countries, the sources said.

The TPP countries held a four-day ministerial meeting through last Friday on the Hawaiian island of Maui, but fell short of securing a broad agreement due to gaps over intellectual property and dairy liberalization issues.