All Venezuelan citizens were called on Thursday to participate in military exercises as the country prepares for a supposedly imminent invasion by the United States, according to dpa. Venezuelan Defence Minister Vladimir Padrino Lopez called on all Venezuelans to participate in the drills, to be organized by the armed forces throughout the country under the slogan "2016 Independence," which will take place Friday and Saturday. "Venezuela is threatened," Padrino Lopez said on state television. "This is the first time we are carrying out an exercise of this nature in the country. In terms of national reach, it's going to be in every strategic region." Maduro announced the exercises earlier this week after pledging to prolong his government's special emergency powers. On Tuesday he accused the United States of plotting an invasion of the South American country and claimed that the US military had flown a spy plane over Venezuela last week. The country, which has the world's largest oil reserves but also the world's highest inflation, has been in deep crisis because of a bitter conflict between the socialist President Nicolas Maduro and the National Assembly, which is dominated by the opposition. Maduro has declared a state of emergency and has given new powers by decree to the military and militias controlled by the socialists. Meanwhile, the Venezuelan National Assembly formally requested the secretary general of the Organization of American States (OAS) to activate the Inter-American Democratic Charter. The National Assembly, in which the opposition holds a majority, asked OAS Secretary General Luis Almagro to take action "before it is too late." In a letter to Almagro, the National Assembly urged him to act given "the process of dismantling democratic institutions and to prevent the humanitarian crisis from worsening in health and food as well as exponentially increasing the risk of violence." Activating the Inter-American Democratic Charter would set in motion a formal OAS assessment of the situation in Venezuela followed by diplomatic initiatives. If those initiatives fail, it could result in the suspension of Venezuela's OAS membership. The opposition has held a majority in the National Assembly since legislative elections on December 6. As part of diplomatic efforts to diffuse the situation, Spain's former prime minister Jose Luis Rodriguez Zapatero met with opposition leader Henrique Capriles and other representatives of the opposition coalition Democratic Unity Roundtable (MUD) on Thursday. Zapatero had previously also met with Maduro.