WASHINGTON — The renegotiation of the North American Free Trade Agreement sputtered forward on Tuesday as officials from the United States, Canada and Mexico concluded their second round of talks with plenty of pleasantries but little major progress to announce.

After five days of discussions in Mexico City, trade negotiators from the three countries said they were encouraged by the talks’ cooperative tenor and remained confident that they could reach a deal by the end of the year.

“I am pleased to report that we have found mutual agreement on many important issues,” Robert E. Lighthizer, the United States trade representative, said during a briefing with reporters at the conclusion of the talks. “Our work continues at a record pace.”

In a joint statement, Mr. Lighthizer and his counterparts — Canada’s foreign affairs minister, Chrystia Freeland, and Mexico’s secretary of the economy, Ildefonso Guajardo Villarreal — said that they had hashed out new ideas and consolidated existing proposals into a single text that will be the basis for future negotiations. The third round of Nafta talks begins on Sept. 23 in Ottawa, Ontario.