The world's biggest network in nuclear proliferation has been broken with the exposure of a top Pakistani scientist, the US secretary of state has said.
The presidential pardon had huge public support
Colin Powell said he would be speaking to the Pakistani president to ensure no remnants of the network were left.
On Wednesday, Abdul Qadeer Khan - the man who gave Pakistan the nuclear bomb - publicly confessed leaking nuclear secrets to Iran, Libya and North Korea.
A day later, Pakistan's "national hero" was pardoned by the Pakistani leader.
"The biggest (proliferator) is now gone and so we don't
have to worry about proliferation from Mr AQ Khan or his network. And this is a success for the international
community," Mr Powell told reporters in New York.
He said he would talk to President Pervez Musharraf by telephone over the weekend, during which he would also raise the issue of the pardon.
United Nations Secretary General, Kofi Annan, described the pardon as "odd", but said the important thing was the assurances Mr Musharraf had given about fighting proliferation.
"Obviously it is a very difficult situation that he has to
deal with - he is dealing with a national hero," Mr Annan told reporters.
Mr Annan called on governments to exchange information to stop the black market in nuclear technology.
He endorsed comments by the head of the International Atomic Energy Agency (IAEA), Mohammed ElBaradei, who said on Thursday that the case of Dr Khan, was the tip of the iceberg.
But while Pakistan has said it will co-operate with the UN watchdog, Mr Musharraf has said he would not allow an inspection of Pakistan's nuclear programme.
The BBC's Jon Leyne in Washington says there is scepticism that Dr Khan acted on his own and there will be private pressure from the US for its ally to provide all the facts.
On Friday, a senior Pakistani official involved with the investigation into the scandal told AFP news agency that Dr Khan could spend the rest of his life under virtual house arrest.
"It is a conditional pardon and Khan knows he would be jailed if he tries to proliferate again in any way," the official said.
More than 15 people from the nuclear enrichment facility that Dr Khan used to run, Khan Research Laboratories, are still being questioned.