The United States and 10 other countries are pushing to strike a deal on a regional free trade agreement known as the Trans-Pacific Partnership by the end of the year, and possibly as soon as a regional leaders meeting in Bali in October.

Negotiators from the United States, Canada, Mexico, Australia, New Zealand, Chile, Peru, Vietnam, Malaysia, Brunei and Singapore are wrapping up the sixteenth round of talks on the TPP pact this week in Singapore.

To reach a deal in the three-year-old talks by the Asia Pacific Economic Cooperation (APEC) summit meeting in Bali, here are some of the tough issues they have to resolve:

AGRICULTURE

The United States is under pressure from domestic dairy groups not to open the U.S. market to additional imports of those farm goods. But every item that Washington takes off the table gives other countries an excuse not to make market-opening concessions in their own sensitive sectors.

U.S. dairy producers are particularly worried about New Zealand, one of the world's largest dairy exporters.

Canadian farmers want to keep domestic "supply management" programs that limit imports of dairy, chickens and eggs.

Japan, which could ask to join the negotiations, is expected to try to maintain its barriers on rice imports and potentially a long list of other farm goods.