UNITED NATIONS - US President Barack Obama shook hands with Cuban President Raul Castro at the United Nations on Tuesday in a rare one-on-one meeting between the former Cold War foes as they work toward improving relations after decades of animosity.Castro, in the first speech at the UN. by a Cuban president since his older brother Fidel addressed the Millennium Summit in 2000, said on Monday the two countries can normalize ties only after Washington ends its trade embargo and returns the Guantanamo US naval base to Cuban control.Obama told the UN on Monday he was confident the US Congress would eventually lift the embargo. His administration has said it does not intend to return the naval base, though it is working hard to close the controversial prison there.Castro and Obama stunned the world last December by announcing detente. On July 20, Washington and Havana restored diplomatic relations after a break of 54 years.The two men and their delegations met on the sidelines of the United Nations General Assembly. They showed an easy rapport, rising out of their seats to shake hands while Obama paused to button his suit coat.Obama and Castro have only interacted a handful of times before, including a meeting at the Summit of the Americas in Panama earlier this year, a phone call last year when they first agreed to jumpstart the US-Cuba relationship, and a phone call last week.