By David Ljunggren and Adriana Barrera
OTTAWA, Sept 25 (Reuters) - Canadian Prime Minister Justin Trudeau on Monday predicted some tough days ahead for negotiators trying to modernize the NAFTA trade pact and declined to say whether he thought the talks could meet a year-end deadline.
Officials from the United States, Mexico and Canada are in Ottawa for the third of seven planned rounds of talks. The U.S. delegation has yet to present its proposals on some of the toughest issues, prompting concerns the process to update the 1994 pact could drag on longer than planned.
"The negotiations are still under way and of course there will be more difficult discussions in some cases than others," Trudeau told a televised news conference in Toronto.
Asked whether he was concerned the talks might not end on schedule, he replied: "The negotiations move forward at a certain pace and we respect that reality."
U.S. trade negotiators will only partially unveil new text in Ottawa on modifying a key chapter on investment under the North American Free Trade Agreement, two well-placed sources said on Sunday.
U.S. President Donald Trump, who frequently describes the treaty as a disaster, is threatening to walk away unless major changes are made.
Canadian officials say it is still possible to meet the year-end deadline although they concede there are significant uncertainties about the timetable.
Canada's chief negotiator on Sunday said he did not expect the U.S. side to present detailed proposals in Ottawa on major issues such as dispute settlement, the dairy sector and tougher rules for North American content on autos.
Trudeau said Ottawa's team of officials was "moving forward in good faith" and repeated a promise to defend Canada's system of tariffs and import restrictions put in place to defend its domestic dairy sector. The U.S. industry dislikes the measures and wants to see them whittled down.
Kenneth Smith, Mexico's chief negotiator, told reporters late on Sunday that "we feel there is a positive environment in the negotiations."
Canadian Foreign Minister Chrystia Freeland, U.S. Trade Representative Robert Lighthizer and Mexican Economy Minister Ildefonso Guajardo - the three top officials driving the NAFTA modernization - will meet in Ottawa on Tuesday and Wednesday, the last two days of the third round. (Reporting by David Ljunggren; Editing by Paul Simao)