Pfizer Chief Executive Officer Ian Read said that the pharmaceutical company is highly unlikely to consider another “corporate inversion” due to the Obama administration’s efforts to halt these offshore tax deals.

“The administration has made it clear they will do whatever it takes to stop an inversion,” Read said at a conference Thursday, according to Bloomberg. “Nothing is off the table, but the inversion would have to be so clean as to be almost impossible in the present environment.”

An inversion is when a U.S. company merges with a foreign company and reincorporates the merged company overseas for tax purposes. Pfizer has unsuccessfully tried to participate in this type of transaction twice.

The company had attempted to merge with British pharmaceutical company AstraZeneca, but AstraZeneca rejected Pfizer’s offer in 2014.

Then last fall, Pfizer and Irish-based Allergan announced plans to merge, only for the proposed $160 billion combination to be terminated in April after the Treasury Department took new actions to curb inversions.

While Read essentially ruled out another inversion, he said that Pfizer is still willing to consider larger merger deals. 

“If you believe you can reorganize your research into productive smaller units, there is a logic to consolidation of the industry by taking out duplicative expenses,” particularly if the two companies can generate dramatic cost savings, Read said, according to Bloomberg.