US President George W. Bush appointed John Bolton ambassador to the United Nations, bypassing the Senate where his nomination stalled amid charges the blunt diplomat would hurt US credibility.

"This post is too important to leave vacant any longer, especially during a war and a vital debate about UN reform," Bush said during a public appearance with Bolton, whom he said had "my complete confidence."

Bolton's appointment comes at a time when the world body is embarking on a debate about sweeping reforms, including new permanent UN Security Council members, and faces possible debates over Iran's and North Korea's nuclear programs.

Opposition Democrats had used procedural delaying tactics to block a confirmation vote on Bolton, who can now serve at the world body until a new US Congress convenes in January 2007 after elections in November 2006.

The critics had pointed to Bolton's unabashed anti-UN statements in the past; his harsh management style as undersecretary for arms control and international security during Bush's first term; and charges that he pressured intelligence analysts to support his views.

Bush's Republicans in the Senate never mustered the 60 votes needed to break through procedural delaying tactics that indefinitely put off a final confirmation vote on the controversial nomination.

"America has now gone more than six months without a permanent ambassador to the United Nations," said Bush. "So today I've used my constitutional authority to appoint John Bolton to serve as America's ambassador to the United Nations."

"I am prepared to work tirelessly to carry out the agenda and initiatives that you and (US) Secretary (of State Condoleezza Rice) Rice direct. We seek a stronger, more effective organization, true to the ideals of its founders, and agile enough to act in the 21st century," said Bolton.

UN Secretary General Kofi Annan said he looked forward to working with Bolton, telling reporters: "We will work with him as we worked with other US permanent representatives."

But he warned that "an ambassador always has to remember that there are 190 others who will have to be convinced, or the vast majority of them, for action to take place."

Democratic Senator John Kerry, Bush's rival for the White House in 2004, acknowledged Bush's constitutional right to make such an appointment but condemned it as "the wrong decision."

"It only diminishes John Bolton's validity and leverage to secure America's goals at the UN," Kerry said in a statement. "This is not the way to fill our most important diplomatic jobs."

Senator Chris Dodd, a senior Democrat on the foreign relations committee, said Bush "has done a real disservice to our nation by appointing an individual who lacks the credibility to further US interests at the United Nations."

Bolton wants Iran's nuclear program referred to the UN Security Council for possible sanctions and favors a hard line against the Stalinist regime in North Korea, which has admitted possessing nuclear weapons.

Hours after the announcement, White House spokesman Scott McClellan warned that the United States would seek UN Security Council action on Iran if the Islamic Republic resumed uranium enrichment.

A firm supporter of the March 2003 invasion of Iraq, Bolton raised eyebrows when he told AFP in June 2004 that the United States would not oppose the creation of a civilian nuclear program in Iraq under certain conditions.

Bolton has been a strong critic of the United Nations in the past, opposing US participation in UN peacekeeping missions and fiercely critical of the disastrous US intervention in Somalia in 1993.

In 2002, he signed the letter informing Annan that the United States would have nothing to do with the International Criminal Court.

Bolton was sworn in shortly after Bush's announcement and traveled immediately to New York to take up his duties, officials said.

PHOTO CAPTION

John Bolton speaks after being installed as the permanent Ambassador to the United Nations for the US by George Bush in the Roosevelt Room of the White House. (AFP)