U.S. President George W. Bush was dealt a blow Thursday when a Senate committee refused to endorse his choice for the next ambassador to the United Nations, John Bolton.

All 10 Republicans on the Senate foreign relations committee voted to send the controversial nomination to the full Senate, while all eight Democrats voted no.

However, they took the rare step of sending it without endorsement after a key Republican senator opposed the nomination, describing Bolton as arrogant and bullying.

John Bolton at the U.S. Senate foreign relations committee on Capitol Hill, Monday. (AP photo)
John Bolton at the U.S. Senate foreign relations committee on Capitol Hill, Monday. (AP photo)

"This is not behaviour that should be endorsed as the face of the United States to the world community at the United Nations," said Senator George Voinovich of Ohio.

"It is my opinion that John Bolton is the poster child of what someone in the diplomatic corps should not be."

Bolton, who is now the top arms control official in the U.S. State Department, has been a long-time critic of the United Nations.

He has also been accused of bullying subordinates and tweaking and exaggerating intelligence information on weapons of mass destruction to please the administration.

"It is my opinion that John Bolton is the poster child of what someone in the diplomatic corps should not be."

The committee's refusal to endorse Bolton is seen as an embarrassment to Bush just six months into his second term.

As soon as the president nominated the outspoken conservative in March, Democrats attacked the choice.

The Senate committee vote was delayed for three weeks after four Republican members also opposed the nomination – but only Voinovich remained steadfast.

"This United States can do better than John Bolton," Voinovich told the committee on Thursday.

His opposition would have caused a 9-9 defeat, since a majority is needed to win.

But the committee acted on a suggestion by Voinovich that they send the nomination to the Senate without the traditional endorsement.

Voinovich said Bolton would be fired if he were in the private sector.

He told reporters he would vote against Bolton in the full Senate.