South Korea is closely watching North Korea over the possibility it may launch another intercontinental ballistic missile (ICBM) as soon as Saturday when it celebrates the anniversary of its founding.
Seoul's Unification Ministry spokeswoman Eugene Lee on Friday said Pyongyang could potentially conduct its next ICBM tests this weekend or around October 10, another North Korean holiday marking the founding of its ruling party.
North Korea has previously marked key dates with displays of military power, but now its tests appear to be driven by the need to improve missile capabilities.
After an intensive exchange of views in phone calls with Chinese president Xi Ping, French President Emmanuel Macron on Friday called on the international community to put more pressure on North Korea to bring the country back to the negotiating table. Both leaders stressed the international community's condemnation of North Korea's "provocations."
North Korea carried out its sixth and the most powerful nuclear test to date on Sunday in what it claimed was a detonation of a thermonuclear weapon built for its ICBMs. The country tested its developmental Hwasong-14 ICBMs twice in July and analysts say the flight data from the launches indicate that when perfected, the missiles could cover a broad swathe of the continental United States, including major cities such as Los Angeles and Chicago.
The ICBMS fired in July were configured to reduce ranges and avoid other countries. But South Korean officials say the next launches could be conducted at angles close to operational as the North would seek to test whether the warheads survive the harsh conditions of atmospheric re-entry and detonate properly.
In Washington, President Donald Trump on Thursday reiterated that military action is "certainly" an option against North Korea, as his administration tentatively concurred with the pariah nation's claim to have tested a hydrogen bomb
"Military action would certainly be an option," Mr Trump said at a White House news conference. "I would prefer not going the route of the military, but it's something certainly that could happen."
A senior administration official said the US was still assessing last weekend's underground explosion but so far noted nothing inconsistent with Pyongyang's claim.
When pressed on whether he could accept North Korea having nuclear weapons but being "contained and deterred," Mr Trump replied, "I don't put my negotiations on the table, unlike past administrations. I don't talk about them. But I can tell you North Korea is behaving badly and it's got to stop."
Last month, North Korea fired a powerful new intermediate range missile, the Hwasong-12, over northern Japan for the first time - an exercise leader Kim Jong-un called a "meaningful prelude" to containing the US Pacific island territory of Guam and called for his military to conduct more ballistic missile launches targeting the Pacific Ocean.
Meanwhile, Sweden has urged its citizens not to make unnecessary trips to North Korea.The announcement by the Swedish foreign affairs ministry came hours after Mexico's government declared North Korean ambassador Kim Hyong Gil as persona non grata and ordered him to leave the country within 72 hours in response to Sunday's nuclear test.
The United States has already banned Americans from travelling to North Korea following the death of Otto Warmbier, a 22-year-old college student from Ohio who was released from North Korea in June in a coma after being detained there for more than a year.
Sweden has had diplomatic relations with North Korea since 1973. The Swedish Embassy in Pyongyang also provides consular services for the United States, Australia and Canada.
South Korean experts say that the launch was Pyongyang's attempt to make missiles flying over Japan an accepted norm as it seeks to test new projectiles in conditions close to operational and win more military space in a region dominated by enemies.
Kim, a third-generation dictator in his 30s, has conducted four of North Korea's six nuclear tests since taking power in 2011. His military has maintained a torrid pace in testing weapons, which also include solid-fuel missiles built to be fired from road mobile launchers or submarines.
In accelerating his pursuit of nuclear weapons targeting the United States and allies South Korea and Japan, Kim is seen as seeking a real nuclear deterrent to help ensure the survival of his government and also the stronger bargaining power that would come from it.
Washington, Seoul and Tokyo have been pushing for stronger sanctions to punish Pyongyang over its nuclear activities, such as denying the country oil supplies. China and Russia have been calling for talks, saying sanctions aren't working against North Korea.