Come off the fence

Title :When Will China Come Off the Fence?

Investigators probing the sinking of the Navy corvette Cheonan have apparently discovered a smoking gun -- pieces of a propeller from a torpedo believed to have sank the vessel -- that implicates North Korea. They compared the collected pieces with a North Korean torpedo sample that was retrieved in the West Sea seven years ago and also analyzed traces of gunpowder found in the wreckage of the Cheonan, a government official said. The government is to announce the results of the investigation on Thursday.

The next task is to gain the support of the international community to come up with effective sanctions against North Korea. U.S. President Barack Obama spoke on the phone with President Lee Myung-bak on Tuesday and said the U.S. trusts and supports South Korea's response and investigation. Obama pledged to send Secretary of State Hillary Clinton to Seoul for close consultations about a response. Cooperation with Washington will prove a decisive factor in effectively implementing additional UN sanctions, bolstering joint military exercises, searching North Korean vessels on the high seas and freezing the North's overseas accounts.

Please explain to me what "come off the fence" means in this context.
Source : http://english.chosun.com/site/data/html_dir/2010/05/19/2010051901318.html