Kim Yong Chun told a national meeting war could break out at any time because of demands by South Korea and the United States to curtail the North's nuclear program, South Korea's Yonhap news agency reported.
The minister said intelligence indicated Seoul and Washington had plotted "madcap maneuvers for mounting a surprisingly preemptive strike" on the North.
He repeated a declaration made several times since 2009 that any fighting would be brief.
"If the U.S. imperialists and the South Korean group of traitors finally ignite a war against the (North), its revolutionary armed forces will ... wipe out the aggressors at one blow," he said.
Apart from the nuclear proliferation issue, Seoul is demanding apologies for two incidents last year that killed 50 South Koreans. The first was the sinking of a South Korean ship and the second involved the shelling of a disputed border-area island.
In a bid to resume nuclear de-escalation talks, former U.S. President Jimmy Carter plans to visit Pyongyang as a negotiator this week and Chinese nuclear envoy Wu Dawei is scheduled to visit Seoul, the report said.
North Korea walked out of the last six-nation nuclear talks in 2009.