Ukrainian President Viktor Yushchenko has sent a letter to U.S. President Barack Obama thanking him for his country's active participation in the operations to release the Ukrainian cargo ship Faina and its crew from pirate captivity.

"I express sincere gratitude to all the servicemen and representatives of the United States who were taking part in this operation, which was completed on February 12," Yushchenko said in his letter, the presidential press service reported on Friday.

The president expressed confidence that the U.S. participation in this long and complicated operation had played a significant role in guaranteeing the security of the Faina's crew and cargo, and contributed to the success of the mission.

"I am sure that the relations between Ukraine and the United States will continue developing in a spirit of friendship, mutual support and strategic partnership," Yushchenko said.