Moon's condemnation of the North's missile launch followed a statement from the UN Security Council which threatened fresh sanctions against the communist North.

"We will sternly deal with the North, together with the international community," he said.

The new South Korean leader also noted the country's military remained fully prepared to counter any military provocations from the North.

"Over the past few months, our political landscape has changed dramatically. I believe such changes could take place peacefully and democratically because our military firmly ensured our security," the president said.

The president also reaffirmed his earlier pledge to expand the defense budget and modernize the country's weapons system.

"I will make it my personal mission to build a sound nation, which is responsible for its own defense, defense that is not only in words but in real capability," he said.

Moon has said he will gradually increase the defense budget to 3 percent of the country's gross domestic product from the current 2.4 percent.

"Governments are limited, but our nation lives on forever. The military's defense posture must not be relaxed even for a moment despite a change of the president. We must all be responsible for our defense, and so we must all work to enhance our defense capabilities," the president said. (Yonhap)