DUBLIN — Treasury Secretary Janet L. Yellen joined world leaders in Rome this weekend to declare the dawn of a new international tax order. On Monday, she traveled to Ireland to offer assurances to one of the countries that benefited most from the old one.

Through a series of events in the capital city, Yellen and Irish Finance Minister Paschal Donohoe insisted that Ireland was strongly positioned to thrive economically even as it agrees to a new 15 percent minimum corporate tax rate that will force the nation to abandon its long-prized 12.5 percent corporate tax rate.

Ireland’s low rate has for decades attracted a number of large U.S. firms, particularly technology and pharmaceutical companies, to relocate divisions or even headquarters to Dublin or surrounding areas. This led to futile complaints from U.S. and other global leaders that Ireland was encouraging tax avoidance. Now, all that could change.

“Was the low corporate tax rate one reason [multinational firms] came? I guess I would have to imagine yes. But it’s not the only reason,” Yellen told the American Chamber of Commerce Ireland, the trade group for U.S. businesses located in Ireland, at the Shelbourne Hotel. She added of the deal: “It won’t change this country’s status as one of the best places to do business in the world.”

Ireland reluctantly but ultimately did join more than 100 other countries in agreeing to the new minimum tax rate. It now stands to prove a key test case for Yellen’s promise that these new rules will usher in an era in which countries compete through talent and innovation, rather than by cutting their corporate rates to ever-lower levels. Leaders of the Group of 20 nations affirmed their support for the new global tax pact on Saturday, and each country must implement the rules on its own.

Despite Yellen’s assurances, unease in Ireland remains over the scope of the new changes and whether they will hurt an economy highly dependent on the kind of multinational firms targeted by the new international tax accord.

Ireland resisted signing on to the global tax pact for months. Officials warned the agreement could hurt the local economy and lead to a decline in government revenue. Irish reporters peppered Yellen and Donohoe with questions on Monday about whether the agreement was being imposed on Ireland by more powerful competitors against its will.

Donohoe told Yellen at the outset of negotiations that Ireland’s low corporate tax rate was so fundamental to its economic identity that virtually any stranger on Dublin’s Grafton Street could probably identify it accurately if asked. Yellen recounted the conversation on Monday.

Microsoft, Apple and Pfizer are among the companies that have benefited from Ireland’s tax system over recent years, showing the allure of the accounting regime. A Microsoft spokesman said in a statement that the company has had a presence in Ireland for three decades and complies with all tax laws. An Apple spokesman said in a statement that the company was the largest in the world and had long supported the international tax agreement. Spokespeople for Pfizer did not immediately return a request for comment.

In a move probably even more significant than the corporate rate increase, the deal will revamp global taxing authority to grant more taxable revenue to countries where large amounts of sales are occurring — rather than where company headquarters are located. That change is likely to benefit countries with big markets and lots of consumers, such as France, while hurting countries like Ireland, according to Seamus Coffey, an Irish economist at University College Cork.

Ireland’s Department of Finance has found that as much as 20 percent of the nation’s corporate tax revenue could be affected by part of the new global tax pact, which is intended to affect only large multinational firms. Corporate income tax paid by U.S. multinationals is three times as high in Ireland as a percentage of the economy as it is in any other country, including the United States itself, according to data provided by Coffey.

“Ireland’s 12.5 percent rate has been the main calling card to attract investment,” said Michael McCarthy Flynn, a tax expert at Oxfam Ireland. “Before the negotiations, the Irish government was acting like this was the end of the world because this has been portrayed as a key part of our competitive advantage.”

Ireland has lacked the type of commercial and financial hub that other European countries use to draw in foreign investment to cities such as London, Paris and Milan. The country was hit hard during the Great Recession in 2008 and 2009, and its low tax rate allowed it to draw in foreign companies and rebuild.

Beyond one of the lowest corporate tax rates, Ireland’s government has also provided a series of other business-friendly incentives, such as allowing multinational corporations to shift huge sums of profit through Irish channels to tax havens such as those in the Caribbean without incurring major taxes. U.S. multinational corporations that poured into Ireland create directly or indirectly more than 300,000 jobs, in a country with only about 2 million workers.

But changes to the global tax order have made it all but inevitable that Ireland’s unique tax arrangement will face new pressures.

Congress in 2017 enacted a minimum tax on U.S. multinationals’ foreign subsidiaries as part of the GOP tax law, which limited how much American firms in Ireland and elsewhere abroad could reduce their tax bills. Congressional Democrats are likely to increase that minimum rate to 15 percent and broaden its scope as part of the Biden administration’s economic agenda.

The United States also put pressure on Ireland to support the global pact, in part because any single country in the European Union could have blocked that entire body’s implementation of the international tax agreement. Yellen on Monday denied that she “cajoled” Irish officials into taking the deal, with leaders in both parties arguing Irish leaders decided they were better off by participating in negotiations than watching from the sidelines.

Ireland, for instance, won a change to the pact striking the language specifying that the new global minimum would be “at least” 15 percent. (Standing next to Donohoe on Monday, Yellen said she does not expect there to be reconsideration of a higher minimum.) And key questions remain unresolved about how the deal will work, with particular uncertainty over the formula for redistributing new revenue from taxes on firms without physical presences. Ireland may be more likely to influence those decisions as a partner to the new deal.

“I am absolutely confident our country will be competitive — will keep jobs — from its strength and position of legitimacy inside the global architecture,” Donohoe told reporters on Monday.

Some experts worry the deal will not do enough to curb international tax avoidance. Low-tax countries like Ireland could still choose to offer tax breaks and other incentives that would effectively fail to arrest the “race to the bottom,” allowing tax competition to persist in a new form. Most firms in Ireland will be exempt from the new minimum, which will apply only to companies with revenue exceeding more than 750 million euros ($868.4 million) per year. Some countries had sought a new global minimum tax of 21 percent.

“Ireland has been successful insofar as they have successfully lowered global ambition — not something to celebrate,” said Sorley McCaughey, a tax expert at Christian Aid Ireland.

But Yellen argued the agreement represents a step in the right direction to a fairer economic playing field. Ireland has invested heavily in public education in recent years and, after Brexit, is an attractive hub for U.S. businesses looking for a foothold into the European Union where English is the dominant language. Those are the kinds of factors — rather than the corporate tax rate — that should determine Ireland’s economic fate, as the deal enables countries on both sides of the Atlantic to raise more revenue, Yellen said.

“Instead of asking, ‘Who can offer the lowest tax rate?’ [the agreement] will allow us to ask, ‘Which nation can offer the best physical and technological infrastructure, and most importantly, the most talented workers?” Yellen said to a packed crowd on Monday at Dublin Castle. “Both Ireland and the U.S. are well positioned to win that race.”