Washington said Monday it has no option but to seek to isolate Pyongyang further.

‘‘What’s left to us is to continue to increase pressure on the North Korean regime and we are looking at how to best to do that, both bilaterally and with our partners going forward until they (North Korea) get the message. We are going to further isolate this regime,’’ U.S. State Department spokeswoman Victoria Nuland said.

Some outside experts worry that Pyongyang’s next move will be to press ahead with a nuclear test in the coming weeks, a step toward building a warhead small enough to be carried by a long-range missile.

Despite inviting further isolation for his impoverished nation and the threat of stiffer sanctions, Kim Jong Un won national prestige and clout by going ahead with the rocket launch.

At a memorial service on Sunday, North Korea’s top leadership not only eulogized Kim Jong Il, but also praised his son. Kim Yong Nam, president of the Presidium of North Korea’s parliament, called the launch a ‘‘shining victory’’ and an emblem of the promise that lies ahead with Kim Jong Un in power.

The rocket’s success also fits neatly into the narrative of Kim Jong Il’s death. Even before he died, the father had laid the groundwork for his son to inherit a government focused on science, technology and improving the economy. And his pursuit of nuclear weapons and the policy of putting the military ahead of all other national concerns have also carried into Kim Jong Un’s reign.

In a sign of the rocket launch’s importance, Kim Jong Un invited the scientists in charge of it to attend the mourning rites in Pyongyang, according to state media.

The reopening of the mausoleum on the anniversary of the leader’s death follows tradition. Kumsusan, the palace where his father, Kim Il Sung, served as president, was reopened as a mausoleum on the anniversary of his death in 1994.

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