Nicolas Maduro is the one opposed to sanctions relief.
Think about it: sanctions are just the perfect justification. There's nothing quite so flexible, encompassing and revolutionary as being the target of U.S. Treasury sanctions. Everything can be explained under the purview of sanctions. Lack of food? Unemployment? No gasoline? Derelict hospitals and crumbling infrastructure? Malnutrition? Teachers striking? Power cuts? All of that, and more, happens because of sanctions. Like the Cuban dictatorship, chavismo has not lost, but reaffirmed the credibility of its now 24 year old criminal regime thanks to sanctions.