WASHINGTON - President Donald Trump's administration is mobilizing U.S. diplomats to lobby against a U.N. resolution calling on Washington to lift its decades-long embargo on Cuba, in part by sharing details of Cuba’s support for Russia’s war in Ukraine, according to an internal State Department cable seen by Reuters.

As part of the administration's campaign, U.S. diplomats will tell countries that the Cuban government is actively supporting Russia's invasion of Ukraine with up to 5,000 Cubans fighting alongside Moscow's forces.

The October 2-dated unclassified cable sent to dozens of U.S. missions directed American diplomats to urge the governments to oppose the non-binding resolution, which has passed in the U.N. General Assembly by wide margins year after year since 1992.

Officials at the Permanent Mission of Cuba to the United Nations did not immediately respond to a request for comment for this story.

Last year, the General Assembly adopted the resolution with 187 countries voting in favor. The United States and Israel were the only countries that voted against it, while Moldova abstained.

Since returning to office in January, Trump has doubled down on sanctions, returning Cuba to a U.S. list of state sponsors of terrorism, tightening financial and travel restrictions and sanctioning third-country nationals who host Cuban doctors.

Trump has also recently toughened his stance towards Moscow, threatening financial penalties against buyers of Russian oil and allowing U.S. intelligence agencies to share information with Ukraine to help its attacks on energy assets inside Russia.

The cable said that the U.N. resolution was "incorrectly" blaming the United States for Cuba's problems which it said were caused by Cuba's "own corruption and incompetence." It added that the objective of this push was to demonstrate the administration's opposition, significantly reducing the number of "yes" votes.

""No" votes are preferred but abstentions or absent/not voting are also useful," the cable said, adding that Washington needed "allies and like-mind...