A new ferry between isolated North Korea and Russia docked for the first time at the Pacific port of Vladivostok on Thursday, May 18, in spite of U.S. calls for countries to curtail relations with Pyongyang over its nuclear and missile programs, Reuters reports.

The launch of the weekly service linking Vladivostok and the North Korean port of Rajin also came despite North Korea's test-firing of a new type of ballistic missile on Sunday that landed in the sea near Russia.

The ferry's Russian operators say it is purely a commercial venture, but the service's launch coincides with what some experts say is a drive by North Korea to build ties with Moscow in case its closest ally China turns its back.

The service is pitched at Chinese tourists wanting to travel by sea to the Pacific port of Vladivostok, according to the operators.

China has no ports on the Sea of Japan, so traveling to North Korea and on to Vladivostok is the quickest way of reaching Vladivostok by sea.

"It's our business, of our company, without any state subsidies, involvement and help," Mikhail Khmel, the deputy director of Investstroytrest, the Russia firm operating the ferry, told reporters.

The United States has been discussing possible new U.N. sanctions on North Korea with China, which disapproves of North Korea's development of nuclear weapons and ballistic missiles to deliver them, but remains its main trading partner.

Washington is looking to toughen U.N. sanctions to cut off Pyongyang's sources of funding and to block smuggling of materials needed for its weapons programs.

Russia, especially the port of Vladivostok, is home to one of the largest overseas communities of North Koreans, who send home much-needed hard currency.