WASHINGTON (AP) — Trump administration officials and Canadian negotiators worked into Wednesday night, trying to strike a deal that would keep Canada in a North American trade bloc with the United States and Mexico.

"Teams are remaining here this evening, working late into the night," Canadian Foreign Affairs Minister Chrystia Freeland told reporters as she entered a meeting with U.S. Trade Rep. Robert Lighthizer. "They will report back to us in the morning."

Last week, the U.S. and Mexico reached a preliminary agreement to replace the 24-year-old North American Free Trade Agreement. But those talks excluded Canada, the third NAFTA country.

Freeland flew to Washington last week for four days of negotiations to try to keep Canada within the regional trade bloc.

The U.S. and Canada are sparring over issues including U.S. access to Canada's protected dairy market and American plans to protect some drug companies from generic competition.

Freeland expressed optimism late Wednesday.

"We are making good progress," she said. "We continue to get a deeper and deeper understanding of the concerns on both sides."