South Korea's unification minister said Sunday now is not the time to talk about dialogue with North Korea, stressing the need to keep the pressure and sanctions on the North over its nuclear and missile provocations.

Unification Minister Hong Yong-pyo said that more extensive pressure should be put on North Korea to make the reclusive nation change its course toward denuclearization.

"For our goal of peaceful unification, now is the time to maintain sanctions and pressure if we want to move toward that goal," Hong said at a press conference.

"I think that we can open a door when we believe that an exit will lead to peace. This is not the time for that," he said.

His remarks came amid growing speculation that North Korea may conduct a fifth nuclear test or launch a medium- or long-range missile ahead of its party congress slated for early May.

North Korea has launched missiles and rocket projectiles since early March in an apparent show of defiance against stronger U.N.

sanctions punishing the North for its fourth nuke test in January and long-range rocket launch in February.

On Saturday, the North fired what appeared to be a submarine-launched ballistic missile in waters off its northeast coast. Last month, it test-fired what looked like an intermediate-range Musudan ballistic missile though this launch ended in failure.

The policymaker said that North Korea seems to be behaving more recklessly compared with the past when it followed a brinkmanship strategy of ramping up tensions and then stepping back without going over the edge.

"We need different strategies and responses to deal with North Korea as Pyongyang is not what it used to be," Hong said, stressing the need to make the North realize that costs far outweigh benefits when it develops nuclear weapons.

Touching on the upcoming party congress, the minister expressed doubts that the party would yield its intended results.

North Korea is ramping up efforts to prepare for the first congress of the ruling Workers' Party of Korea (WPK) in 36 years in early May. Pyongyang is pushing its people to work harder under the "70-day campaign of loyalty," ahead of the event.

"North Korea appears to hope that the party congress will open the so-called Kim Jong-un era. But I think that the party event can become a poison for the North, not medicine," Hong said.

There is a possibility that the North could hold the party congress without high-profile foreign guests as more countries are believed to seek to shun it amid toughened international sanctions.

"There is no noticeable movement from China (over its possible attendance). Countries like Cambodia appear to consider sending working-level officials," said a senior official at Seoul's unification ministry, asking not to be named. "It seems that there will be only a few countries that will send officials."

In October last year, China sent Liu Yunshan, who ranks fifth in China's ruling Communist Party hierarchy, to a military parade to mark the 70th anniversary of the WPK's founding.

But it is not clear whether Beijing will send its official to the North's party congress, given their chilly ties following a series of the North's provocations.

The official said that there is a high probability that North Korea could carry out its fifth nuclear test ahead of the party congress. (Yonhap)