In the letter, Maduro said that US President Donald Trump has been waging "a campaign of harassment and threats" against the Latin American country since August, Xinhua reported.
The deployment of more than 14 US warships and 15,000 troops in the Caribbean Sea is creating a climate of tension that could disrupt regional security and affect energy supplies, he said.
Maduro denounced the US attempt to seize Venezuela's crude oil reserves, warning that it poses a direct risk to the balance of the global market.
Venezuela will remain "firm" in defending its energy resources and will not yield to external pressure, he said, adding that in the past, military interventions in oil-producing countries have led to instability and adverse consequences for both consumers and exporters.