North Korea may make surprise proposals to South Korea this year including reunions of separated families in a bid to break up the united international sanctions front, a report showed Thursday.

In 2017, North Korea would seek to improve inter-Korean ties by taking advantage of political transitions in South Korea, the report by the Korea Institute for National Unification showed, referring to a possible earlier-than-expected presidential election in the South.

The report said that North Korea may make proposals that Seoul cannot easily reject -- reunions of families torn by the 1950-53 Korean War or holding of high-level talks.

"By making such proposals, Pyongyang will likely demand Seoul lift its May 24 unilateral sanctions and resume operation of the now-shuttered Kaesong Industrial Complex," it said.

From the humanitarian perspective, the issue of separated families is the most pressing one, but the North has refused to hold more reunions, claiming that South Korea is to blame for the suspension of such events.

The May 24 sanctions refer to Seoul's punitive measures taken in 2010 to punish North Korea for the torpedoing of the South Korean warship Cheonan.

South Korea also shut down the factory zone in the North's border city of Kaesong in February 2016 following North Korea's nuclear and missile tests earlier last year.

"We should bear in mind that North Korea's top strategic goal is to create cracks in the global sanctions regime," the KINU report said.

The United Nations Security Council imposed tough sanctions twice last year in response to its fourth and fifth nuclear tests and missile launches conducted by the reclusive country.

The report said that North Korea will continue to advance nuclear weapons programs, focusing on strengthening its capacity to make boosted fission bombs.

North Korean leader Kim Jong-un said in his New Year's message that the country has entered the final state of preparations to test fire an intercontinental ballistic missile in the latest sign that it will not abandon its nuke and missile programs.

"It cannot be written off that North Korea will push ahead with another nuclear test to raise the level of its explosive yield to around 50 kilotons," it said.

South Korea's defense ministry said the yield of the blast in North Korea's nuclear test in September 2016 is presumed to have been at around 10 kilotons, the largest ever conducted by country. (Yonhap)