U.S. Treasury Secretary Jack Lew said on Thursday that easing Greece’s fiscal surplus targets is one of several different ways that the country could achieve a more sustainable path for its debt, but declined to specify an alternative target.

“You can do that in a variety of different ways,” Lew told a news conference about how Greece’s debt can be more sustainable and satisfy European lenders and the International Monetary Fund. “I’m not going to take a hard view on where Greece and institutions should end up. Except that in the end, it has to work.”

Euro zone lenders are requiring that Athens reach a primary budget surplus of 3.5 percent of gross domestic product in 2018, a level that the IMF says is too high and cannot be realistically achieved.