The U.S. Treasury Department unveiled new measures this week to slow the pace of deals by which American companies cut their taxes by moving elsewhere, clamping down on the practice known as inversions.  The rules, which apply to deals that close on September 22 or after, include a prohibition on “hopscotch” loans that let companies access foreign cash without paying U.S. taxes and impose new curbs on actions that companies can take to make an inversion transaction qualify for favorable tax treatment.

“We’ve recently seen a few large corporations announce plans to exploit this loophole, undercutting businesses that act responsibly and leaving the middle class to pay the bill,” President Obama said in a statement this week.

Treasury Secretary Jack Lew, in turn, told reporters that the new measures should slow the pace of such deals, and that he is still looking at other possible changes.  The new rules will, among other things, restrict a company’s tax-free access to cash outside U.S. borders. Lew said he wanted to make companies think twice before considering inversions, in which companies seek foreign addresses though their executives and major operations remain in the United States.

Congress deadlocked on legislation to curb inversions, and the Democratic-back bills have not come to a vote.  Lawmakers, who left Washington to campaign for the November 4 election have not shown much interest in writing bipartisan legislation to curtail inversions.  Most Republicans say the issue should be addressed as part of a broader revamp of the U.S. tax code.

Some analysts believe Burgers King’s move to take over Tim Hortons Inc in Canada and shift the headquarters of Burger King Worldwide Inc. to Canada was the catalyst for the U.S. Treasury’s action.  “The final tipping point for lawmakers on whether to introduce the changes to the tax code was likely the prospective deal between Burger King and Tim Hortons, which would have seen the iconic American fast-food restaurant become Canadian,” said analyst Jasper Lawler of CMC Markets in London.

Burger King last month agreed to buy Tim Hortons in a deal valued at about $12 billion, including debt, making it the largest-ever leveraged buyout in U.S. history.  The new enterprise, based in Canada, would include more than 18,000 restaurants in 100 countries.

Burger King and Tim Hortons at least for now do not expect the new rules to scuttle their deal.  “We are moving forward as planned,” a Tim Horton spokesman said.  “This deal has always been driven by long-term growth, not tax benefits.”