The UN's outgoing human rights commissioner, Mary Robinson, says she was prevented from continuing in the job because of pressure from the US, which she has accused of neglecting human rights during the war against terrorism.

"I am not somebody just to walk away," Ms Robinson said. "If I had been hard-pressed, I would have stayed, [but] there seems to have been strong resistance from just one country."

Outgoing U.N. High Commissioner for Human Rights Mary Robinson gestures during an interview with Reuters in Geneva July 29, 2002. Robinson will be succeeded by Brazilian Sergio Viera de Melo September 1, 2002. REUTERS/Jean-Marc Ferre

Her remarks came a week after the UN secretary general, Kofi Annan, announced her replacement, a veteran Brazilian diplomat described yesterday as "somebody who doesn't run afoul of the big powers".

Ms Robinson, 57, a former Irish president and only the second person to hold the post of high commissioner for human rights, has been a vocal critic of the US since September 11 - not least over Washington's decision against granting prisoner of war status to the detainees at Guantanamo Bay in Cuba.

"I believe that the emphasis has been on the war on terrorism, and that there has been a blurring of the edges and a lack of precision," Ms Robinson said in an interview with Reuters. "A lack of precision means a lack of protection."

The climate had become "much more difficult for human rights", she said.

Tension between the commissioner and the Bush administration pre-date military action in Afghanistan, and turned particularly rancorous over the world conference against racism in Durban, South Africa, which almost collapsed under the weight of a Syrian-led campaign for delegates to declare Israel a racist state.

But this is the first time Ms Robinson has blamed Mr Annan's decision not to extend her tenure on lobbying by Washington.

Her replacement, Sergio Vieira de Mello, a career UN diplomat with a background in humanitarian relief and peacekeeping, seems certain to adopt a less outspoken style.

"He's a very diplomatic operator, somebody who doesn't run afoul of the big powers," a UN official told the Guardian. "And somebody who is very effective in that way up to now."

Asked if Mr Vieira de Mello was expected to avoid confrontation with the US, the official said: "The short answer is yes, and the long answer is yes."

But a spokesman for the secretary general said Mr Annan had taken the decision not to reappoint Ms Robinson "independently".

"It's not one state or one body of states saying this is what we want - otherwise, frankly, you'd have a very different-looking UN," he said.

© Guardian Newspapers Limited 2002