(Refiles to add official's name in last paragraph)
* More than 150 states have ratified pact to ban atom bomb tests
* But approval by U.S. and seven other holdouts also needed
* U.S. Senate rejected it in 1999; Obama plans new push
By Fredrik Dahl
VIENNA, Oct 4 (Reuters) - Chile, the Philippines and the Netherlands are among countries lobbying for their candidates to head an international body set up to monitor a planned global ban on nuclear weapon tests, diplomats said on Thursday.
Senior officials from Burkina Faso and Mongolia are also seeking the job as executive secretary of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) in a vote expected later this month.
"It is quite open. There are five good candidates" with nuclear and disarmament experience, one European diplomat said about the campaign to succeed Tibor Toth, an Hungarian who now holds the post. Another envoy in Vienna predicted a close race.
The successful candidate will take over at a potentially important time for the future of the treaty, with proponents hoping the United States will finally ratify it and give it a much-needed momentum towards becoming international law.
It is one of eight countries - together with China, India, Pakistan, Israel, Iran, North Korea and Egypt - whose approval is needed for the pact that was negotiated in the 1990s and has so far been ratified by 157 states to take effect.
U.N. Secretary General Ban Ki-moon last week called on them to ratify it, saying they were "failing to live up to your responsibility" as a member of the international community.
"There is a direct link between ending nuclear testing and eradicating nuclear weapons," he said.
The United States and China are two of the world's five officially recognised nuclear weapons states, together with Britain, Russia and France.
India, Pakistan, North Korea and Israel are also outside the separate nuclear Non-Proliferation Treaty, the 1970 pact to prevent the spread of nuclear arms. Iran is part of the NPT but the West accuses it of seeking to develop a capability to build atomic bombs. Tehran denies the charge.
Proponents say U.S. ratification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), rejected by lawmakers in 1999, could encourage others to follow.
The administration of U.S. President Barack Obama - who seeks a second term next month - said last year it was preparing a push for approval, arguing the country no longer needs to conduct atom tests but does need to stop others from doing so.
More than 2,000 nuclear tests were carried out between 1945 and 1996, when the CTBT opened for signature, most of them by the United States and the then Soviet Union.
Since then, only India, Pakistan and North Korea have conducted such blasts, supporting the view by its backers that the treaty has already had a major impact.
At the time of the U.S. Senate vote on the CTBT 13 years ago, opponents argued that a permanent end to testing could erode the reliability of the U.S. nuclear arsenal. The United States last carried out a nuclear test two decades ago.
The Arms Control Association, a Washington-based research and advocacy group, said nuclear testing was a "dangerous and unnecessary vestige" of the Cold War. But, "without positive action on the CTBT, however, the risk that one or more states could resume nuclear testing will only grow", it added.
The CTBTO has a verification regime to detect any nuclear blasts, including more than 280 monitoring facilities across the globe - a system that helped track radioactive particles from Japan's Fukushima nuclear accident in 2011.
Toth's successor is due to be picked at an Oct. 22-23 meeting in Vienna of the more than 180 states which have signed the CTBT. In the absence of a consensus, a vote will take place.
(Editing by Alison Williams)