In phone calls to Washington lawmakers and Obama administration officials, the chief executive of the largest drug maker in the nation had a surprising message: A deal that would allow the company to move its headquarters to Ireland was actually good for the United States.

The Scottish-born chief executive of Pfizer, Ian C. Read, told them that a merger with Allergan, the maker of Botox that is based in Dublin, would significantly cut Pfizer’s tax bill and give it more cash that it could invest in the United States and ultimately add jobs, according to people briefed on the calls. He made the calls in recent days as the two companies were hammering out a $152 billion deal.

Monday’s announcement of the deal — the biggest merger in 15 years — has revived a fierce public debate over whether mergers that allow a company in the United States to relocate to a lower-tax country are, in fact, good for America.

Pfizer, founded by German immigrants in Brooklyn in 1849, is becoming the biggest company yet to shed its American citizenship to lower its taxes. While not structured as what is known as an inversion, it achieves the same goal of a lower tax rate abroad.