WASHINGTON — Officials negotiating a 12-nation Pacific trade agreement continued talks Saturday, hoping to clear some final hurdles and announce the long-elusive completion of an agreement.

Since high-level talks on the Trans-Pacific Partnership began Wednesday in Atlanta, officials from the U.S., Japan, Canada and nine other countries appeared to have made significant headway in overcoming two of three major obstacles in the way of the biggest free-trade deal in a generation.

Reports from Atlanta on Friday indicated that trade officials had agreed on rules involving the foreign content of automobiles and auto parts. Industry sources said they saw a compromise on market access for dairy products, which are highly protected in Canada and other countries.

But people monitoring the talks at a hotel in Atlanta said there were still sharp differences over patent lengths for certain complex drugs known as biologics. The U.S. is said to be seeking a standard of eight years of intellectual property protection for these drugs before generic substitutes can be made.

Most of the dozen Trans-Pacific Partnership countries provide for five or fewer years of such protection, and officials are reluctant to extend patent lengths that could delay patient access to cheaper generic drugs, and also strain government health budgets.

The Trans-Pacific Partnership is an effort to link closely the 12 nations, which make up 40 percent of the world economy. The U.S. joined the talks in 2008, and since there have been multiple rounds of negotiations involving hundreds of tariff items and rules on various aspects of trade and investment.