– The excitement in some U.S. and foreign diplomatic circles about the rise of Juan Guaido and an expectation for the fall of Nicolas Maduro has been replaced by frustration over the Venezuelan leader’s staying power and concerns about Russian and Chinese meddling, according to multiple diplomatic sources.

Maduro’s hold on Venezuela has led diplomats, foreign leaders and some Washington officials to consider that, barring military action, Maduro may be able to follow in the footsteps of other authoritarian leaders who have stayed in power despite crushing sanctions.

“Maduro has definitely shown he is more resilient than what people thought. That’s a fact,” said a diplomat from Latin America who was not authorized to speak publicly about the regional strategy. “If you think about what the administration said about ‘this is the end, this is the end,’ and yet Maduro is still there.”

Foreign diplomats in Washington say they got caught up in expectations raised by some in the Trump administration that Guaido would take over the government and so are disappointed that Maduro’s regime has not yet fallen. Confidence that Maduro’s fall was guaranteed has now turned more to hope that he will — and concern he may not.

“There was this euphoric reaction that we all felt that it was the end of Maduro,” said Fernando Carrera, Guatemala’s foreign minister in 2013 and 2014. “I felt it. I was part of that group. I thought Maduro is gone. But, no, Guaido couldn’t make it happen. The Trump administration couldn’t make it happen. And the Chinese and Russians have raised the stakes too high.”

Trump’s special envoy for Venezuela, Elliott Abrams, said: “We do not have the ability to predict exactly when regimes like this will fall, but we do have the ability to analyze, and we are confident Maduro’s regime will eventually come to an end. The endgame for him should be to leave Venezuela, and the sooner the better, because his own situation is only going to decline the longer he clings to power and the more misery will be in the country.”

Diplomats from the region say economic pressure, mainly U.S. sanctions, may not be enough to dislodge Maduro if the people don’t rise up.

Maduro has been able to keep territorial control of the South American nation despite recognition by more than 50 nations, including the U.S., of Guaido as interim president, crippling oil sanctions and paralyzing banking restrictions.

The Venezuelan generals the U.S. sees as essential to controlling the populace have stuck by Maduro despite veiled U.S. threats of military action. The sanctions must be given time to have an effect, some argue. Venezuela’s oil sector accounts for as much as 70 percent of the Maduro government’s income.

Another diplomat noted that the banking sanctions — imposed in retaliation for the arrest of Guaido’s chief of staff — could also have an almost equally devastating impact on Maduro’s ability to keep his base. “It will be hard for Maduro to pay his public servants,” said another diplomat from the region, who spoke on the condition of anonymity. “That will hurt a lot.”

A senior administration official said the U.S. and regional allies remain committed to seeing Maduro leave and democracy restored. “The momentum remains firmly on the side of Interim President Juan Guaido and the National Assembly,” the official said.

Meanwhile, the Trump administration continues to increase the pressure.