By Ian Talley

BADEN-BADEN, Germany--U.S. Treasury Secretary Steven Mnuchin rebuffed a concerted push by world finance chiefs Saturday to disavow protectionism, fanning fears that the Trump administration's pursuit of an "America First" policy could ignite global trade conflicts.

Instead of hammering out a compromise that allayed those fears, finance ministers and central bankers from the Group of 20 largest economies ended two days of negotiations with a joint statement that papered over their trade debate and largely reiterated a series of longstanding promises to boost growth, avoid currency devaluations and ward off threats to the global economy.

"Sometimes you have to limit yourself at such meeting to not asking too much of one partner; you can't ask too much of him anyway because he would then simply not agree to it," said German Finance Minister Wolfgang Schäuble. "But I believe this is a result where the [G-20] process can continue well."

He added that Mr. Mnuchin appeared to have "no mandate to negotiate any new or creative wording on trade."

Mr. Schäuble and his counterparts had hoped Mr. Trump's top economic envoy would offer a vision of U.S. trade policy that tempered the most aggressive threats by the president and White House officials, including unilateral tariffs and other punitive sanctions against trade partners.

In failing to secure a written agreement from the U.S. that would repeat past G-20 vows to reject protectionism in all its forms, many officials said they were departing confused about where the new administration will ultimately land on trade policy.

The Treasurysecretary advanced his boss's view, promoting "free and fair trade."

"The United States has been treated very, very unfairly by many countries over the years," Mr. Trump said in Washington on Friday, ahead of a meeting with German Chancellor Angela Merkel, who chairs the G-20 this year. "That's going to stop."

Despite the pressure Mr. Mnuchin faced from most of the G-20 membership, Washington showed it still holds significant sway as the world's consumer of last resort: The G-20 adopted a pledge to promote "fairness" as it pursued economic growth.

G-20 officials said they see both a new administration struggling to get up and running and competing power centers with different views on trade.

"Nobody knows what the endgame is," a senior G-20 official said. "Either the meeting is several months too early or it's perfect timing," the official said, giving the G-20 an opportunity to help temper U.S. policy before it is cemented.

Investors are still confused, for example, about the administration's dollar policy, having been given different signals from Mr. Trump and his lieutenants.

Asked who markets should heed, Mr. Mnuchin said: "They should listen to the president first and listen to me as well."

Evidence that it may just be too soon for the U.S. to offer the G-20 anything substantive on trade, financial regulation, tax overhauls and other policies, Mr. Mnuchin is relying on senior civil servants to conduct much of the detailed negotiations at the meeting. The secretary's international diplomats have only recently been nominated and still must go through a lengthy confirmation process.

If trade czar Peter Navarro and Steve Bannon, a top Trump adviser and self-described economic nationalist, have their way, many official fear the White House could trigger a trade war. The administration has advocated applying unilateral actions that eschewa rules-based multilateral order, including submission to the World Trade Organization's authority.

Others in the administration, including Mr. Mnuchin and Gary Cohn, director of the National Economic Council, hold a more internationalist view of the world. If they prevail in guiding administration policy, many G-20 officials see fiery campaign rhetoric being tamed in the coming months.

Mr. Schäuble said that Mr. Mnuchin appeared to have "no mandate to negotiate any new or creative wording on trade" and while all G-20 partners agreed on opposing protectionism, it wasn't always clear what they meant with this.

Some countries are worried that failure to temper aggressive trade policy could not only trigger a round of retaliatory tariffs and a rise in other trade barriers that would damage global growth, it could exacerbate geopolitical tensions.

Earlier this week, for example, U.S. Secretary of State Rex Tillerson raised the option of a pre-emptive strike against North Korea because Pyongyang's nuclear-missile program poses a growing threat to U.S. ally South Korea. China traditionally is able to strong-arm Pyongyang into cooling hostilities. But if U.S.-China trade tensions escalate, Beijing may in future be less cooperative in playing that role, some analysts warn, raising the risk of a dangerous regional conflict.

"Global cooperation and pursuing the right policies can help achieve strong, sustained, balanced and inclusive growth," International Monetary Fund Managing Director Christine Lagarde said after the meeting. "The wrong ones could stop the new momentum in its tracks."

Many officials are also concerned the U.S. administration, in targeting immigration and trying to bring manufacturing back to the U.S., is focusing on the wrong problems.

The U.S. needs to better adapt to automation, they say. Some economists argue the rise of robots mayhave been a stronger factor in America's manufacturing decline and related job losses over the past two decades than China's trade policies.

"Higher-skilled workers are much more likely to benefit from innovation and economic openness," Ms. Lagarde said ahead of the G-20 meeting. "This calls for greater efforts to equip lower-skilled workers with the tools they need to seek and find better-paying jobs."

Andrea Thomas contributed to this article.

Write to Ian Talley at ian.talley@wsj.com

(END) Dow Jones Newswires

March 18, 2017 12:34 ET (16:34 GMT)

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