(CNN) Venezuelan opposition leader Juan Guaido is calling more openly than ever for US assistance, as he continues to seek fresh elections in the country.

In a letter posted early Monday, Carlos Vecchio -- Guaido's appointed ambassador to the US -- requested a meeting between the US Southern Command and Guaido's representatives. The May 11 letter was addressed to US Adm. Craig S. Faller, who heads the Southern Command and who had previously voiced support for Guaido's movement on the official Twitter account of the Southern Command.

Venezuela's opposition movement would "welcome strategic and operational planning so that we may fulfill our constitutional obligation to the Venezuelan people," Vecchio wrote to Faller. It did not call for military action specifically.

For months, the US has refused to rule out military action in support of Guaido's movement. However, US President Donald Trump has also urged caution among senior advisers moving forward, and expressed frustration that some aides were openly hinting at a US military intervention in Venezuela, according to officials familiar with the matter.

Guaido is Venezuela's National Assembly President, recognized as the country's legitimate interim president by more than 50 countries, including the United States. As momentum slows in the nationwide protests that he regularly organizes, Guaido has begun to eye new strategies for political change in the country.

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