Ambassador Zalmay Khalilzad will replace John Negroponte, who left Iraq last year to assume a Washington post as US Director of National Intelligence,
Foreign Affairs Committee chairman Richard Lugar said on Friday.
Khalilzad had been the US ambassador to Afghanistan for a year-and-a-half when President George Bush nominated him to his new post. He was warmly encouraged by Republicans and Democrats in hearings last week.
Khalilzad's nomination was approved on Wednesday by Lugar's committee, clearing the way for the full Senate to vote on his appointment.
The diplomat will lead one of the largest US embassies in the world, with a staff of some 1160 under his authority.
Khalilzad takes over the US embassy in Baghdad at a critical juncture, as the new Iraq government faces a deadline of drafting a constitution by 15 August and holding a referendum on the document on 15 October.
National elections to choose a permanent Iraqi government by 15 December would also take place on his watch.
In comments made on Thursday during a farewell news conference in Kabul, Khalilzad said: "My premise is that failure is not an option. There is too much at stake."
"We have to isolate those who have no interest in Iraq's success, whose agenda is a global agenda, who would like to bring about a civil war in Iraq to back their unholy agenda and then to promote a war of civilisation."
Osama on the loose
Khalilzad said last week he was "disappointed" that Osama bin Laden remained at large, but pledged the al-Qaida leader would be captured.
Khalilzad believes Osama bin
Laden is alive and evading capture
An Arabic speaker and Muslim, who was born in Afghanistan, Khalilzad has served in various capacities in the US Departments of State and Defence, as well as with the National Security Council, and in academia.
He was also an adviser to the giant oil company Unocal during Taliban rule in Afghanistan.
The Senate also confirmed a score of other nominations on Thursday, including that of Craig Stapleton as ambassador to France.
Stapleton was ambassador to the Czech Republic from September 2001 to the end of 2003.
He was, for 18 years, president of Marsh and McLennan Real Estate Advisors.