Japanese Prime Minister Naoto Kan has reportedly ordered all members of the Cabinet to be on standby in the Tokyo area during the South Korea-U.S. joint military drill in the Yellow Sea that begins Sunday.

Kyodo News said Kan ordered the Japanese Cabinet to be within one hour of their ministries at all times in case an emergency occurs during the South Korea-U.S. joint military exercises.

Kan reportedly gave the order to prepare for a potential additional provocation by North Korea, who earlier vowed to respond “mercilessly” to any threat to its sovereignty.