Ernst & Young’s renegade U.S. auditors are demanding that the firm examine the financial health of its potential offspring as they block a breakup of the global accounting firm. 

Julie Boland, EY’s U.S. chair and managing partner, called for rethinking the split, which has been in the works for more than a year. The U.S. audit partners want a bigger piece of the firm’s lucrative tax business. 

“The questions we need to resolve affect the capabilities and financial strength of both businesses,” said Ms. Boland, who was tapped to lead the global auditing business after the breakup. 

Ms. Boland two weeks ago sent shock waves through the Big Four firm by announcing a pause to the plan to split its auditing and consulting arms. The call for a rethink by EY’s U.S. arm has created a rift between the U.S., the firm’s largest business, and the rest of the world.

Ms. Boland rejected suggestions that a few people on her executive committee were upending a blueprint supported by most of EY’s 13,000 partners. 

“There’s different points of view,” she said. “This is incredibly complex. People are asking the right questions, and we’re making sure we’re getting those questions answered.”

Carmine Di Sibio, EY’s global chairman and chief executive, told employees he is confident the deal will proceed.

Photo: Margarita Corporana for The Wall Street Journal

Her support for a review reflects a split among EY leaders that threatens to scuttle the deal. Carmine Di Sibio, EY’s global chair and chief executive, told employees after the pause was announced he had a “high degree of confidence” the deal would move forward, according to a copy of the message reviewed by The Wall Street Journal. 

That confidence doesn’t appear shared by the U.S., which is by far the biggest firm in EY’s 390,000-person global network, contributing around 40% of global revenue. 

“We remain committed to a separation that meets the fundamental principles of creating two purpose-led inspirational businesses,” Ms. Boland said.

The principal U.S. demand is for the new audit-focused firm to have more of EY’s lucrative tax practice than the one-quarter share envisaged in the original proposal, according to people familiar with the matter.

But the Americans also want EY to take a fresh look at the ambitious profit and revenue targets set for the consulting business, given the economic downturn, according to people familiar with the matter. A revenue target of 25% annual growth under the original breakup plan has already been softened to 19%, the people familiar with the matter said. 

Ms. Boland told U.S. partners and employees in the fall EY needed to be sure it could achieve the “aggressive revenue plans, aggressive profitability goals [for the new consulting business]…based on what we’re seeing in the market today,” according to a copy of an internal webcast reviewed by The Wall Street Journal. 

The U.S. firm has in recent months canceled a planned midyear bonus for staff and cut back on expenses, as it seeks to maintain its profitability ahead of the planned sale of the consulting arm.

Any reduction in the targets set for the consulting company could reduce its likely value in a sale, as would a reduction in its share of the tax practice. 

EY’s leaders planned to sell a 15% stake in this business to the public for around $11.5 billion. That money, together with $18.5 billion of new borrowing by the company, would be used mainly to fund seven-figure cash windfalls to audit partners, to compensate for giving up the fast-growing consulting arm. 

EY’s leaders have set an internal deadline of weeks to either resolve the impasse or abandon the deal, according to the people familiar with the matter. 

Top executives are concerned EY’s bumpy execution of its plan could damage the firm’s reputation as a top-tier adviser to global companies, the people familiar with the matter said. Another worry is the damage to morale from the continuing uncertainty and feuding over the firm’s future.

“This is so embarrassing get it together EY,” one person wrote recently on the EY section of employee-website Fishbowl. 

“Just ready for it to be done with,” another person commented. “I will go [to whichever of the two new firms] they want and if I don’t like it I’ll leave.”

EY’s leaders gathered in New York last week to try to work out a deal, one of the people familiar with the matter said. The two-day meeting at their new U.S. headquarters at One Manhattan West brought together the heads of EY’s global network, its European and Asia Pacific regions, and its U.S. and U.K. firms, the person familiar with the matter said.

The talks didn’t lead to a breakthrough. Instead, EY leaders have continued horse-trading over how to allocate its thousands of tax professionals, according to people familiar with the matter.

— Alexander Saeedy contributed to this article.

Write to Jean Eaglesham at Jean.Eaglesham@wsj.com