South Korea's senior official on North Korean policy says Pyongyang is mistaken if it thinks preparations for a missile test will squeeze diplomatic concessions from the United States.
Also Washington's current and former envoys to South Korea have repeated warnings that a launch will have very negative consequences.
South Korean Unification Minister Lee Jeong-seok says if North Korea thinks it is gaining diplomatic leverage with a possible missile test - it is wrong.
Lee told lawmakers in Seoul Friday it seems clear that testing a long-range missile will not produce any compromises with the United States.
Instead, he says the best hope Pyongyang has for gaining diplomatic and political rewards is by returning to multilateral talks aimed at ending its nuclear weapons programs.
World leaders have expressed concern for more than a week at intelligence the North is preparing to test fire one of its Taepodong-Two ballistic missiles.
Lee said Friday that the preparations may be a political move - but added that Pyongyang's recent steps indicate it intends to carry out the launch.
U.S. Ambassador to South Korea Alexander Vershbow says the United States has the option to use its advanced defense systems to shoot down a North Korean missile.
He also said a launch would have negative consequences for Pyongyang.
"We will want to take some significant steps to show that business as usual can't continue, and step up our efforts to prevent proliferation by the North of their missile technology."
The United States, Russia, China, South Korea and Japan have been trying for three years to persuade Pyongyang to fulfill its prior promises not to build nuclear weapons, in return for financial and diplomatic benefits.
Pyongyang, however, has refused since last year to return to talks.
One of Vershbow's predecessors, former U.S. Ambassador Donald Gregg, told businessmen in Seoul Friday there are some in Washington who would actually welcome a North Korean missile test - particularly those who support a hard-line policy toward North Korea.
He says a test would provide intelligence about the North's missile capabilities and help to isolate Pyongyang in the international community.
However, Gregg warns that a missile launch would deal a serious blow to the six-party talks.
With the potential for negotiations damaged, he says Pyongyang will step up its weapons programs.
"The North Koreans will move forward with whatever it is they are doing with missiles. They will become more comfortable with it. They will become more technically proficient. And the price of getting them to give up those capabilities will rise higher."
Gregg says the United States should talk to the North directly. Senior North Korean diplomats asked for such a dialogue earlier this week.
Washington, however, says it will only deal with North Korea in the six-party talks.