European Union leaders observe a minute of silence to honor the victims of the attacks in Paris, at the G-20 Summit in Antalya, Turkey, Monday, Nov. 16, 2015. From left to right, Spain's Prime Minister Mariano Rajoy, German Chancellor Angela Merkel, European Council President Donald Tusk, France's Foreign Minister Laurent Fabius, European Commission President Jean-Claude Juncker, British Prime Minister David Cameron, and Italian Prime Minister Matteo Renzi. (AP)

The leaders of the world’s richest and most powerful nations on Monday pledged for the first time not to conduct cyber economic espionage, a move that could one day greatly reduce the theft of hundreds of billions of dollars’ worth of commercial secrets by foreign governments to benefit their countries’ own industries.

The agreement reached at the Group of 20 conference in Antalya, Turkey, marks the first major, high-level international consensus aimed at reducing tensions in cyberspace. Last year, the Justice Department announced indictments against five Chinese military hackers for allegedly stealing secrets from solar-power firms and steelmakers.

The agreement follows a pledge by Chinese President Xi Jinping at his summit meeting with President Obama in September that his country would refrain from such activity.

Xi’s vow was noteworthy because Beijing until that point had made no distinction between commercial cybertheft to profit a nation’s industries and espionage for traditional political and military purposes.

But the expansion of that agreement to include Russia and France — two other major countries that U.S. intelligence analysts say conduct cyber economic espionage — as well as a majority of the world’s major economic powers is important, officials and analysts say.

Christopher Painter, State Department coordinator for cyber issues, called the group’s action “very significant” in establishing global rules of responsible behavior in cyberspace.

The United States, which spies on economic targets but not, officials say, to benefit U.S. firms, has long sought international consensus on establishing such a norm. The G-20 leaders agreed that “no country should conduct or support [cyber]-enabled theft of intellectual property, including trade secrets or other confidential business information, with the intent of providing competitive advantages to companies or commercial sectors.”

“Words have an effect, and people have now committed not to do this,” said James A. Lewis, a cyber-policy expert at the Center for Strategic and International Studies. If a country is caught violating the pledge, he said, “you respond.” It could be through economic sanctions, which the United States was preparing this summer to impose on Chinese firms, or indictments. Or it could be through other measures.

The leaders also affirmed that international law applies to cyberspace, among several other norms. That means a commitment to following rules of proportionality and discrimination in cyber-operations, such as not intentionally targeting systems that can harm civilians during an armed conflict. Earlier this year, a smaller group of nations’ “governmental experts” on cybertechnology endorsed that view at the United Nations.

The G-20 agreement “elevates and broadens the affirmation” by the U.N. experts, Painter said. Together, he said, he hoped the norms “will lead to greater stability in cyberspace.”