Finance ministers from Group of Seven nations meeting in London on Friday are expected to back President Biden’s call for a global minimum tax on corporate profits, giving him an early win in a grueling diplomatic campaign that is just beginning.

The new minimum tax, one half of a two-pronged global reform effort, is designed to halt a cycle of corporate tax-cutting that has sapped government revenue around the globe. As part of a package deal, negotiators are also wrestling with European demands to tax American technology giants such as Google and Facebook, which earn substantial revenue in countries where they have little physical presence.

Biden catalyzed the global tax debate in late May by proposing a worldwide minimum tax of at least 15 percent, which was lower than many tax specialists had expected. If he can secure agreement from the world’s leading democracies — en route to a broader global consensus later this year — it could eventually produce the most significant global tax shift in decades.

Putting a floor beneath multinationals’ tax bills in other countries would help the president raise the corporate rate at home to 28 percent by reducing the incentive for corporations to continue shifting hundreds of billions of dollars in profits to low-tax venues.

Along with opposition from corporate lobbyists, additional obstacles loom, including objections from low-tax countries such as Ireland as well as likely noncompliance from China and Russia. After more than three decades of factory offshoring, any global minimum levy also might only minimally reshape the map of global production and investment.

“Fundamentally, the goal for all of us is to make sure companies that are multinationals are paying their fair share of taxes,” Deputy Treasury Secretary Wally Adeyemo said in an interview. “Anything we can do to close the gap is going to be a boon to the American economy and business.”

Biden confronts a complex chore, which blends rewriting the tax code’s eye-glazing arcana with the diplomatic puzzle of satisfying the interests of both advanced and developing nations. The varying domestic and global political calendars mean administration officials may end up asking Congress to change U.S. tax law before other nations have acted.

Negotiators are simultaneously wrestling with both the global minimum levy and the challenge of taxing digital companies. Several global bodies such as the G-7 and the G-20 are involved. The U.K., which hosts Friday’s finance minister session and a leaders’ summit in June, insists that the digital and minimum tax issues be resolved in a single bargain. Securing E.U. agreement, meanwhile, requires unanimity among its 27 nations. And the international talks are occurring as the United States gears up to rewrite its domestic tax laws.

Amid all these moving parts, the expected G-7 endorsement “is good news in terms of the possibility of a global agreement,” said Michael Mundaca, U.S. national tax department leader for Ernst & Young. “But it’s still very early.”

Biden’s time-consuming multilateral strategy signals a departure from President Donald Trump’s preference for unilateral tariffs.

The Democrat’s determination to use a tax code overhaul to reset the terms of global commerce is reflected in the addition to his Treasury Department team of several prominent

academic tax specialists, including Kimberly Clausing of Reed College, Rebecca Kysar of Fordham Law School and Itai Grinberg of Georgetown University.

The president’s aim is to shrink the role that tax calculations play in corporate investment decisions, boosting economic efficiency and income. But even some supporters caution that the immediate gains may prove modest.

“We will get some revenue by shrinking the use of tax havens, especially for intangibles, and we will get the benefit of multinationals locating any start-ups in the U.S.,” said Steven Rosenthal, a senior fellow at the Urban Institute. “But I don’t think we’ll see the end of factories and jobs leaving America. To the extent that’s done now, it’s more because of other factors such as technology and wages. It’s not done for tax rules.”

Under the auspices of the Organization for Economic Co-operation and Development (OECD) in Paris, 137 nations have been wrestling since 2013 with the question of how to tax corporations in a globalized, digital economy.

The pandemic’s budgetary impact, coupled with an American president determined to narrow the gap between rich and poor, have given momentum to the idea of a global minimum corporate tax, U.S. officials and tax specialists said.

Governments around the world spent an estimated $16 trillion battling the novel coronavirus over the past year, according to Vitor Gaspar, director of the International Monetary Fund’s fiscal affairs department. All those bills for health care and economic support drove the average country’s public debt to 99 percent of gross domestic product this year, up from 83.7 percent in 2019.

That has left governments thirsty for revenue. Changing the way corporate taxes are collected could harvest between $100 billion and $600 billion annually, according to published estimates.

“The benefits are tremendous. Once we have it, the race to the bottom that is depriving emerging markets and developing countries from revenue is going to stop,” Kristalina Georgieva, managing director of the International Monetary Fund, said recently. “I get a strong sense of confidence that this is going to be done and we would all breathe a sigh of relief when it is done.”

Even without action by other nations, the Biden administration expects to reap more than $533 billion over the next decade by reducing incentives for U.S. corporations to shift assets and incomes abroad, according to the president’s budget proposal released Friday.

The global debate over raising government revenue caps a generation of collapsing corporate tax rates. Since 1980, the global average rate set in national laws, weighted according to economic output, has fallen from more than 46 percent to 26 percent, according to the nonprofit Tax Foundation.

In 2017, the Trump administration lowered the U.S. corporate rate to 21 percent. But what corporations actually pay — the effective rate — is less than 8 percent, according to the congressional Joint Committee on Taxation.

Annual revenue from corporate taxes relative to the size of the economy is now less than one-quarter as large as in 1967, according to the Congressional Budget Office. The Biden administration sees raising the corporate share as an essential way to pay for its “Build Back Better” agenda of infrastructure and social spending.

“We can keep giving every break in the world to corporations and CEOs, or we can raise the corporate tax rate back to 28 percent … which is still lower than it was at any point between World War I and 2017, and they're making trillions of dollars,” the president said Thursday in Cleveland.

Determining how — and how much — to tax corporate earnings has become tougher as companies expanded their cross-border operations and drew greater profits from intangible goods such as software and intellectual property.

Corporate accountants easily shift income on paper to low-tax jurisdictions such as Ireland, the Cayman Islands or Bermuda: 40 percent of the profits multinationals earn outside their home country are “artificially shifted to tax havens,” according to a 2018 study by Gabriel Zucman, an economics professor at the University of California at Berkeley, and Ludvig S. Wier and Thomas R. Tørsløv, both of the University of Copenhagen.

Corporate leaders oppose Biden’s plans. Even as the proposal for a global minimum tax appears to be gaining steam at the G-7, business leaders say that differences in the structure of European and U.S. tax codes — such as which expenses can be deducted from taxable income — make it difficult to imagine implementing a uniform corporate tax.

“All we know is they’re talking about a rate. We don’t know what it applies to. We don’t know how it applies,” said Catherine Schultz, vice president for tax and fiscal policy at the Business Roundtable.

Speaking at a recent Washington Post roundtable, the IMF’s Georgieva said she expected negotiators to continue haggling over the rate for the global minimum as well as potential implementation timetables.

U.S. officials still hope to eventually get a global minimum rate above 15 percent. But the current negotiations represent a balancing act: They need a rate low enough to win wide support but high enough to shrink the incentive for U.S.-based multinationals to engage in profit shifting.

After Friday’s scheduled gathering of finance ministers from the G-7 — the United Kingdom, France, Germany, Canada, Italy, Japan and the United States — the administration’s strategy winds through additional global meetings. Negotiators hope to secure an agreement in principle some time this summer, with a final accord sealed at a Group of 20 leaders summit in Rome at the end of October.

Yet even if a diplomatic agreement is reached, each nation will need to rewrite its tax code through legislation. So Congress will probably vote on the administration’s tax plan before that work is completed.

“They want to push for a tax change domestically at a time when all they’ll have will be political commitments from the OECD countries. Those political commitments are just that. They’re political commitments. They’re not changes in law,” said Brent McIntosh, who was Treasury’s top international official in the Trump administration.

correction

An earlier version of this article said President Biden had lowered his proposal for a global minimum tax rate from 21 percent to 15 percent. He had not initially proposed a 21 percent rate. Rather, that is the U.S.'s current corporate tax rate.