(This January 31 story corrects figures and name in 10th paragraph; Ricardo Colon was initially identified at State briefing as Richard)
WASHINGTON (Reuters) - The U.S. State Department voiced displeasure on Wednesday over North Korean plans to stage a military parade on the eve of the Winter Olympics but assured Americans going to the games that South Korea's security plan considered all contingencies.
"Any citizen of the United States traveling to the 2018 Winter Games can rest assured that the Republic of Korea has a comprehensive security system in place and that the United States government is supporting our ally," Under Secretary of State Steve Goldstein told a briefing.
The Winter Games begin on Feb. 9 in Pyeongchang, South Korea, at a time of high tensions over North Korea's nuclear weapons and missile programs.
After talks to defuse tensions, North and South Korea agreed to field a unified women's ice hockey team and to march their athletes under one flag at the opening ceremony.
Despite its decision to send athletes, North Korea announced it would celebrate the founding of its military on Feb. 8, an event generally marked with a large military parade displaying weapons such as missile launchers.
"While we would prefer that this parade not occur on Feb. 8, it is our hope, and I know the hope of South Korea, that the North Koreans ... will join with all the nations of the world in celebrating the athletes," Goldstein said.
The North Korea monitoring group 38 North said in an analysis on Wednesday that satellite photos showed some 12,000 troops and 110 artillery pieces, tanks and armored vehicles practicing for a parade.
As of Jan. 28 the images showed no signs of ballistic missile launchers, 38 North said, but those vehicles usually only arrive a week or so before the parade. Shelters for missile launchers and other heavy equipment were erected several weeks ago and some may already be hidden from view inside, it said.
U.S. officials said the State Department's Diplomatic Security Service was helping South Korean authorities with security, a role it has undertaken at every Olympics since the 1976 Montreal games.
Ricardo Colon, a Diplomatic Security official, said the service would have about 100 personnel in South Korea, working from the U.S. Embassy and the Olympics venues. They are assisting 242 athletes and as many as 30,000 U.S. citizens.
U.S. security officials said they were unaware of any specific threats and were confident the South Koreans would provide a secure Olympics. They noted Seoul hosted the 2014 Asian games and the 2002 FIFA world cup.
"We're only less than a hundred miles (160 km) from North Korea," said Michael Evanoff, the assistant secretary for diplomatic security. "So we've planned for all contingencies."
(Reporting by David Alexander; Editing by David Gregorio and James Dalgleish)