(Reuters) -OpenAI executives have considered accusing Microsoft ( MSFT ), the company's major backer, of anticompetitive behavior in their partnership, the Wall Street Journal reported on Monday, citing people familiar with the matter.

OpenAI's effort could involve seeking a federal regulatory review of the terms of its contract with Microsoft ( MSFT ) for potential violations of antitrust law, as well as a public campaign, the report said.

Such a move could unravel one of the most pivotal tech partnerships in the fast-growing field of artificial intelligence.

"Talks are ongoing and we are optimistic we will continue to build together for years to come," representatives for the two companies told the WSJ in a joint statement.

OpenAI needs Microsoft's ( MSFT ) approval to complete its transition into a public-benefit corporation. But the two have not been able to agree on details even after months of negotiations, sources said.

The companies are discussing revising the terms of Microsoft's ( MSFT ) investment, including the future equity stake it will hold in OpenAI, according to the sources.

Separately, The Information reported that OpenAI wants Microsoft ( MSFT ) to hold a 33% stake in a restructured unit in exchange for foregoing rights to future profits, citing a person who spoke to OpenAI executives.

The ChatGPT owner wants to modify existing clauses that gives Microsoft ( MSFT ) exclusive rights to host OpenAI models in its cloud, the report added.

Microsoft ( MSFT ) has not agreed to OpenAI's proposed terms and is reportedly seeking additional concessions from the startup, according to The Information.

Both companies did not comment on the reports from the WSJ and The Information.

Microsoft ( MSFT ) invested $1 billion in OpenAI in 2019 to support the startup's development of AI technologies on its Azure cloud platform.

Since then, however, OpenAI has been looking for ways to reduce its reliance on the tech heavyweight. The company plans to add Alphabet's Google Cloud service to meet its growing needs for computing capacity, Reuters reported earlier this month.