Top United States diplomat Marco Rubio bluntly warned Venezuela against attacking its oil-rich neighbor Guyana, brandishing the power of the US military to protect the small South American nation.

Venezuela, whose leftist leader Nicolas Maduro who seems to be despised by the Cuban-American Rubio, has increasingly pushed its claim to the disputed Essequibo region controlled by Guyana, and was accused earlier this month of making an incursion.

Rubio told a joint news conference on a visit to Guyana, noting that there will be consequences for aggressive action.

Asked what the United States would do if Venezuela attacked ExxonMobil oil projects in Guyana, Rubio said: “It would be a very bad day for them.

While in Guyana, Rubio signed an agreement to boost security cooperation with the country including through greater information sharing.

It comes years after Guyana and the United States agreed to joint maritime patrols.