The United States continues to look for "additional ways" to move President Barack Obama's vision for a nuclear-free world forward, the White House said Tuesday, amid reports the administration is considering adopting a nuclear "no first use" policy.

"The president during his landmark 2009 speech in Prague detailed a trajectory to place us on the path to a world without nuclear weapons. In the intervening years, this administration -- through our own actions and by galvanizing the international community -- has achieved progress on a number of fronts," Myles Caggins, an assistant press secretary, told Yonhap News Agency.

Achievements include reducing deployed stockpiles and launchers through New START, which refers to a 2010 nuclear arms reduction treaty between the U.S. and Russia, diminishing the role of nuclear weapons in U.S. security strategy, and securing the Iran deal to stop the proliferation of nuclear weapons, the spokesman said.

"Moreover, we have consistently looked for additional ways to achieve progress on the President's path forward, including by reinforcing what has become a de facto international norm of responsible international behavior against nuclear testing," he said.

The spokesman, however, did not say whether the nuclear no first use policy is under consideration.

A series of security experts have expressed strong concern about abandoning the nuclear preemptive strike option, saying it would send the wrong signal at a time when Russia is flexing its military muscle, China is building up its nuclear forces and North Korea is bent on developing nuclear missiles.

The no first use policy could erode the confidence allies have in the U.S. nuclear umbrella, they said. (Yonhap)