(Adds more comments from German minister)

By Dave Graham

MEXICO CITY, May 19 (Reuters) - Germany's foreign minister voiced support for the North American Free Trade Agreement (NAFTA) during a visit to Mexico on Friday, giving a diplomatic boost to the country ahead of its renegotiation of the accord with the Trump administration.

U.S. President Donald Trump has sharply attacked NAFTA for months, and on Thursday his government triggered the process to start overhauling the deal that binds the United States, Canada and Mexico, potentially ushering in formal talks by mid-August.

Since taking effect in 1994, NAFTA has been a gateway for scores of multinationals to build factories in North America, channeling billions of dollars worth of investment into the region by European companies, many of them German.

Following a visit to Washington this week, German Foreign Minister Sigmar Gabriel told reporters in Mexico City German firms were concerned about the future of the accord, urging the United States to recognize the benefits it had yielded.

"In our view NAFTA is an agreement that doesn't just serve Canada and Mexico, but also the United States," he said at a news conference with his Mexican counterpart Luis Videgaray.

"So we're trying, also via our visits to the United States, to make clear that a fair agreement isn't just in the interests of German companies, but also the United States of America," added Gabriel, who is also Germany's vice chancellor.

Gabriel's visit came ahead of a planned trip to Mexico by Chancellor Angela Merkel on June 9-10, according to two people familiar with the matter, who spoke on condition of anonymity.

According to U.S. data, Germany and Mexico last year both ran trade surpluses of more than $60 billion with the United States, sparking complaints of unfair treatment from Trump, who has threatened aggressive measures to eliminate the deficit.

Germany has given short shrift to Trump's threats, and in January Gabriel said the United States "should build better cars" in response to the New Yorker's claim there were not enough American automobiles on the streets of his home city.

During her visit, Merkel would, alongside economic matters, also address the protection of human rights, press freedom and the fight against organized crime in Mexico, areas of significant concern to both governments, Gabriel said.

Amidst a resurgence in gang violence, Mexico's government is under increasing pressure to better protect the media after a spate of killings of journalists this year that culminated in two separate deadly attacks this week.

(Editing by Lisa Shumaker)