The decision ends months of tensetalks as the European Union had reacted angrily to initial U.S. demands, saying they would breach the privacy rights of its citizens.
The incident comes at a tense time, as Macedonian and Greek diplomats begin talks on an agreement to normalize relations, muddied by a dispute over Macedonia's right to its name.
Lew has irked powerful Republicans like Senate Minority Leader Mitch McConnell during tense negotiations to raise the debt ceiling as well as the final round of talks to avert the fiscal cliff at the end of 2012.