Bernardo Alvarez, a longtime Venezuelan ambassador to the United States who led Hugo Chávez’s diplomats in defending his country’s socialist revolution to skeptical foreign governments, died Nov. 24 in Caracas. He was 60.

His death was announced by Venezuelan president Nicolás Maduro. He did not provide a cause of death.

Mr. Alvarez served as Venezuela’s ambassador to the United States from 2003 to 2010. His tenure came during a period of strained relations between the two countries, but many U.S. officials considered the former college professor a pragmatic diplomat who helped prevent ties between the countries from deteriorating even further.

“He was the last of the moderate Bolivarians,” said Michael Shifter, president of the Washington-based Inter-American Dialogue, which recently hosted Alvarez for an event. “With Bernardo there was always a willingness to engage in dialogue that wasn’t necessarily true of others in the government.”

For the past year, Mr. Alvarez had been serving as Venezuela’s ambassador to the Organization of American States, where he helped stymie a hemispheric push to isolate Maduro for jailing opponents. He also helped quash an opposition campaign to cut short Maduro’s term through a recall referendum.

Maduro said Mr. Alvarez had been reaching out in recent days to President-elect Donald Trump’s transition team in a bid to improve ties with the United States.

Venezuela and the United States have not exchanged ambassadors since 2010. Mr. Alvarez was expelled twice from Washington, in 2008 and 2010, in retaliation for Chavez’s decision to oust U.S. Ambassador Patrick Duddy for allegedly plotting his overthrow and then denying credentials for his named successor.

Bernardo Alvarez Herrera was born Aug. 18, 1956, in Carora, Venezuela, and was a graduate of the Central University of Venezuela. He had a master’s degree in development studies from the University of Sussex in England.

He was a political-science professor at the Central University of Venezuela and held several governmental positions, including in the country’s Ministry of Energy and Mines, before becoming ambassador to the United States.

Mr. Alvarez was also Venezuela’s ambassador to Spain, served as deputy foreign minister and from 2013 to 2015 headed the Chavez-created Bolivarian Alliance of 11 leftist-run Latin America and Caribbean nations.

Information about survivors was not immediately available.