(Adds Roscosmos comments)
By Irene Klotz
CAPE CANAVERAL, Fla., March 25 (Reuters) - Two Russian cosmonauts and a U.S. astronaut blasted off for six-month stay aboard the International Space Station on Tuesday, a partnership unaffected by the political rancor and economic sanctions triggered by Russia's annexation of Crimea.
The Russian Soyuz rocket carrying cosmonauts Alexander Skvortsov and Oleg Artemyev and NASA astronaut Steven Swanson lifted off at 5:17 p.m. EDT/2117 GMT from the Baikonur Cosmodrome in Kazakhstan.
The trip to the space station, a $100 billion research laboratory that flies about 260 miles (418 km) above Earth, was scheduled to take about six hours. However, an unknown problem caused the crew's Soyuz capsule to skip two planned steering maneuvers, delaying the crew's arrival until Thursday.
"The crew is in no danger. The Soyuz (is) equipped with plenty of consumables to go even beyond the next two days, should that be become necessary. Nobody expects that that will be the case," mission commentator Rob Navias said during a NASA Television broadcast.
Russian flight controllers expect to get more information about why the Soyuz's thrusters failed to fire when the capsule flies over ground communications stations later on Tuesday.
"Initial information indicates the problem may have been the spacecraft was not in the proper orientation for the burn," NASA said in a status report posted on its website.
Russia's state television channel Rossiya-24 quoted national space agency Roscosmos as saying the flight of the Soyuz spaceship was now taking place "in a reserve mode" after its orientation engines failed to ignite.
"It's all normal on board," it said.
Docking was tentatively retargeted for 7:58 p.m. EDT/2358 GMT on Thursday.
Several hours before the docking, Soyuz will make a final emergency manoeuvre to enter the orbit of the space station, RIA news agency quoted a Russian space official as saying.
The arrival of Skvortsov, Artemyev and Swanson will return the station to a full six-member crew. The orbital outpost, a project of 15 nations, has been short-staffed since two other cosmonauts and a NASA astronaut returned to Earth on March 11.
The space station partnership, overseen by the United States and Russia, so far has been immunized from the political and economic fallout following Russia's invasion of Ukraine's Crimean peninsula.
"We don't want to see political turmoil and it could ultimately get in the way of our spaceflight, but from the operator standpoint ... this is absolutely a non-issue for us," NASA astronaut Reid Wiseman, who is due to fly to the station in May, said in a CBS News interview on March 18.
"I mean, we're three really good friends climbing into a Soyuz (capsule) to fly into space. All politics aside, there's no doubt it's going to work for us," Wiseman said.
The United States currently pays Russia more than $63 million per seat to fly its astronauts to and from the space station.
The Russian part of the station taps electricity generated by U.S.-owned and operated solar wing panels and supplements its ground-based communications with NASA's orbital satellite network, among other U.S.-provided services.
One of the first orders of business for the newly arriving station crewmembers will be to capture and berth a Space Exploration Technologies' Dragon cargo capsule, which is due to launch on Sunday from Cape Canaveral Air Force Station in Florida.
Two Russian spacewalks are planned during the crew's six-month mission, as well as two or three outings overseen by NASA. (Additional reporting by Maria Kiselyova in Moscow and Dmitry Solovyov in Almaty; Editing by Eric Walsh)