WASHINGTON—Former Minnesota Gov. Tim Pawlenty, a likely GOP White House hopeful, called on congressional Republicans to block an increase in the limit on federal borrowing, and he proposed legislation that he said would prevent a U.S. default on its loans.

In an interview with The Wall Street Journal Sunday and in an appearance on "Fox News Sunday," Mr. Pawlenty challenged even leaders in his own party, who have said Congress must increase the federal debt ceiling rather than risk a default that could send interest rates skyrocketing...