WASHINGTON — An ambitious 12-nation trade accord pushed by President Obama would allow foreign corporations to sue the United States government for actions that undermine their investment “expectations” and hurt their business, according to a classified document.

The Trans-Pacific Partnership — a cornerstone of Mr. Obama’s remaining economic agenda — would grant broad powers to multinational companies operating in North America, South America and Asia. Under the accord, still under negotiation but nearing completion, companies and investors would be empowered to challenge regulations, rules, government actions and court rulings — federal, state or local — before tribunals organized under the World Bank or the United Nations.

Backers of the emerging trade accord, which is supported by a wide variety of business groups and favored by most Republicans, say that it is in line with previous agreements that contain similar provisions. But critics, including many Democrats in Congress, argue that the planned deal widens the opening for multinationals to sue in the United States and elsewhere, giving greater priority to protecting corporate interests than promoting free trade and competition that benefits consumers.

The chapter in the draft of the trade deal, dated Jan. 20, 2015, and obtained by The New York Times in collaboration with the group WikiLeaks, is certain to kindle opposition from both the political left and the right. The sensitivity of the issue is reflected in the fact that the cover mandates that the chapter not be declassified until four years after the Trans-Pacific Partnership comes into force or trade negotiations end, should the agreement fail.