Washington is likely to take the matter to the U.N. Security Council, analysts say, and could tighten its already tough sanctions. Such efforts would struggle without support from China, which can be expected to resist any moves that might threaten the stability of its neighbor.
There also is deep uncertainty about where turning the screw further on North Korea would lead. After the Security Council condemned its previous long-range rocket launch in 2009, North Korea responded by kicking out U.N. nuclear inspectors, pulling out of aid-for-disarmament negotiations and conducting its second detonation of an atomic device.
"At minimum, there has to be a statement of criticism" at the Security Council, said Gordon Flake, a Washington-based Korea analyst. "The question is how North Korea will react, and history suggests it won't react well."
The stakes are higher than they were in 2009 as the potential for tensions on the Korean peninsula to escalate into conflict are greater now than they were then. South Korea's government came under heavy domestic criticism for what was seen as a weak response to a North Korean artillery barrage that killed four people on a front-line island in 2010. Earlier that year, North Korea was believed to have torpedoed a South Korean warship, killing 46 sailors. The North denied responsibility.
North Korea says the missile launch is intended to place an observation satellite into orbit. But the U.S. and others view the launch as a cover for a test of an intercontinental ballistic missile that one day could carry a nuclear warhead.
Crucially for Washington, if the three-stage Unha-3 rocket works, it could demonstrate that North Korea has parts of the United States in its missile range.
The launch would violate both a U.N. ban and an accord the impoverished country reached with Washington on Feb. 29, under which it would freeze nuclear activities and observe a moratorium on nuclear and long-range missile tests in exchange for 240,000 metric tons of food aid.
The launch plans, disclosed a little more than two weeks after the accord was announced, undermined what little faith Washington and Seoul had in North Korea's sincerity about talks on its nuclear program. It also all but squashed the fleeting prospect that the nation would change after the December death of longtime ruler Kim Jong Il.
Obama, facing re-election and accused by opposition Republicans of naivete for reaching out to North Korea, pointedly visited the heavily militarized Korean border last week during a trip to South Korea for a nuclear summit. North Korea's new leader, Kim Jong Un, previously had made the visit from the northern side.
Obama implored the North's leaders "to have the courage to pursue peace," but warned that unless they changed their ways, the country would face "more isolation." But neither he nor other administration officials have said what steps the U.S. will take should North Korea launch the missile.
The U.S. and allies including Japan and South Korea could seek to clamp down further on the North's illicit weapons trade and impose additional financial and banking restrictions that have hurt North Korea in the past.
Fears about the launch have spread farther afield than previously. The Philippines has expressed concern about falling debris. Indonesia says the launch would undermine regional stability. Russia and China, which have long-standing ties with the North — also have urged Pyongyang to rethink its plans. Vietnam has urged North Korea to comply with Security Council resolutions
The breadth of criticism reflects not just recognition that the launch would violate U.N. resolutions, but that this rocket, unlike previous launches, will head not eastward over Japan and into the relatively empty Pacific but toward busier waters off Southeast Asia.
Washington is urging China — North Korea's most important ally and trading partner — to nudge its neighbor into line, but the prospects appear slim. North Korea has promoted the launch as a sign of the nation's strength and progress as it marks the centennial of the birth of its founder, Kim Il Sung. Recent satellite imagery showed preparations under way at the launch site.
The launch also may be an effort to consolidate the authority of Kim's grandson, Kim Jong Un, who is establishing a third generation of dynastic rule.
Park said that while China is doubtlessly frustrated by the North's conduct and has made a stronger public statement than it did before the 2009 launch, its ultimate concern will be to preserve the still-fragile government of Kim Jong Un and prevent a regime collapse on its own frontier.
He also doubted that Washington would risk its own relations with China by taking a new step: penalizing Chinese companies that do business with North Korea.