"The national shipping company of KSA (Kingdom of Saudi Arabia) clarifies that its oil tanker is on her way from the Red Sea to pick up a cargo from the Port of Jose Terminal in #Venezuela for one of its regular customers in India", the Saudi embassy said.
The embassy said the cargo was contracted on 9 January, long before the United States imposed sanctions on Venezuela on 28 January.
It added that the ship's voyage would be completed before the end of the exemption period allowed for winding down business with sanctioned Venezuelan entities.
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The embassy was responding to remarks Rubio made on Twitter on Saturday, when he accused Saudi Arabia’s shipping company of "blatantly trying to undermine US efforts" to support the Venezuelan people.
Rubio has been a vocal supporter of opposition leader Juan Guaido, who on 23 January declared himself to be Venezuela's interim president. Guaido's declaration was almost immediately recognized by the United States and some of its allies.
Russia, China, Mexico, Turkey, Iran and Uruguay have said that they consider constitutionally elected Maduro to be Venezuela's legitimate president.
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In late January, the United States blocked all assets of Venezuela’s PDVSA in its jurisdiction and imposed a ban on deals with the oil company. US Treasury Secretary Steven Mnuchin told reporters that by blocking PDVSA's assets, the United States was taking care of this company "in the interests of the people of Venezuela" and also protecting its own market.