NEW YORK (AP) - A handful of companies pursuing overseas deals that could lower their tax rates are under pressure after the U.S. unveiled rules that would make those deals less lucrative.

NEW YORK (AP) A handful of companies pursuing overseas deals that could lower their tax rates are under pressure after the U.S. unveiled rules that would make those deals less lucrative.

The Treasury Department announced new regulations Monday that would make it less lucrative to pursue a so-called inversion. Under such a deal, an American company buys a foreign firm, then re-incorporates overseas.

The pharmaceutical company AbbVie, based in Chicago, reached an agreement to buy Dublin-based Shire in July for $54 billion.

Shares of both companies sank in Tuesday trading. AbbVie Inc. lost 2 percent in New York trading, while Shire sank 2 percent in London.

The British drugmaker AstraZeneca, considered a likely takeover candidate, slumped 3 percent.

Medtronic Inc., also pursuing an inversion, fell 3 percent.