VIENNA U.S. politicians are showing growing interest in a treaty to outlaw nuclear tests, the head of the agency set up to monitor the ban said on Thursday, but it is uncertain when or whether lawmakers will adopt a pact that they rejected in 1999.
Tibor Toth, executive secretary of the Comprehensive Test Ban Treaty Organization (CTBTO), said approval by the U.S. Senate would be a "game changer" for the landmark treaty that was negotiated in the mid-1990s but has yet to take effect.
"I welcome increased interest in what we are doing," Toth told Reuters in an interview, adding this came from both Democrats and Republicans in the United States.
"In the last six-eight months, each three weeks on average, we had some sort of visit from the United States. We had nearly 10 percent of the U.S. senators in different delegations visiting us."
There is widespread international support for the test ban treaty, which has been ratified by about 155 states, but it cannot come into effect because some nuclear powers like the United States and China have not yet done so.
Proponents say U.S. ratification of the pact -- which Toth said had helped cut the number of tests to two in the last 10 years, both in North Korea, from several hundred in previous decades -- could encourage other holdouts to sign on.
The administration of U.S. President Barack Obama said in May it was preparing a push for approval of the treaty, arguing that Washington no longer needs to conduct such tests but needs to stop other countries from conducting them.
But it has not given a precise time when it would seek a Senate vote on the treaty, which the chamber rejected when fellow Democrat Bill Clinton was president. A two-thirds majority would be needed for approval.
"I think it is important that there is no rushed decision," Toth said, speaking at agency headquarters in Vienna.
Obama, who will seek a second term next year, has made clear he sees the test ban pact as a step toward his vision of a world without nuclear weapons, like the new START arms reduction treaty the Senate approved last year.
"CATCHING THE MOUSE"
Toth said the other countries which also need to ratify the ban for it to enter into force -- India, Pakistan, Israel, Iran, North Korea, Indonesia and Egypt -- should not wait for Washington to act.
Of that group, four states -- India, Pakistan, North Korea and Israel -- are outside the nuclear Non-Proliferation Treaty.
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 and says its nuclear programme is aimed at producing electricity for peaceful purposes.
"I don't think Iran should wait for U.S. ratification, as other countries should not wait for U.S. ratification," Toth said. "This is where Iran can send a strong message."
At the time of the Senate vote 12 years ago, opponents argued that a permanent end to testing could erode the reliability of the U.S. nuclear arsenal. The country last carried out a test nearly 20 years ago.
Some also questioned whether cheaters could be detected.
Toth said "many things" had since changed -- a system to monitor the ban is 80 percent ready and as many as 182 states have signed the treaty -- and that the U.S. administration was now seeking to educate senators about the treaty and its merits.
But asked whether he believed the pendulum was swinging in favour of the ban in the United States and whether there was a growing acceptance that it was needed, he said: "I think the jury is out and I don't want to predict what will come out."
His organisation 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 March.
"It is a system which can catch the mouse," Toth said.
(Editing by Elizabeth Piper)