Lew stressed that the while the U.S. economy is slowly improving, the nation relies on the strength of the EU's economy.
"Our economy's strength remains sensitive to events beyond our shores and we have an immense stake in Europe's health and stability," Lew said in Brussels. "The Unites States has no bigger, no more important economic relationship that it does with Europe."
The trip, the second for Lew since he took the helm at Treasury in February, comes ahead of the expected start of trade talks in June between the the two economies that would, with a free-trade agreement, create a $5 trillion trading bloc.
A U.S.-EU trade deal would that the "conomic relationship can be even more productive as a source of trade, jobs and growth," he said.
The 27-nation EU is seeking ways to boost growth and slow the rising tide of unemployment.
“We have an immense stake in Europe’s health and stability,” Lew said. “I was particularly interested in our European partners’ plans to strengthen sources of demand at a time of rising unemployment."
On Monday he also had meetings with EU Commission President Jose Manuel Barroso, the region's EU's top economic and monetary official, Olli Rehn and European Central Bank President Mario Draghi.
He is scheduled on Tuesday to meet with German Finance Minister Wolfgang Schaeuble in Berlin and France's top finance minister Pierre Moscovici, who announced on Sunday that the French economy is expected to expand at an anemic 0.1 percent rate this year.