US Secretary of State John Kerry has landed in Baghdad in Iraq at the start of a Middle East tour to build support for action against Islamic State.
Mr Kerry is due to meet new Iraqi PM Haidar al-Abadi less than 48 hours after a unity government was agreed.
An inclusive government was a condition for greater US and Nato support in the fight against IS militants who have taken over large parts of the country.
President Barack Obama is due to outline his plans to combat IS later. He said on Tuesday that he had authority to widen military action against IS without the approval of Congress, but said he would still ask lawmakers to endorse the arming of Syrian opposition forces.
IS militants have taken over large parts of Syria and Iraq in recent months and have declared a "caliphate".
In the past month, IS militants have beheaded two US journalists in protest against American airstrikes on its forces in Iraq.
Saudis 'main target'
Mr Kerry's tour is due to continue in Saudi Arabia and other regional capitals, where he is hoping to boost military, political and financial support for the fight against IS.
He is expected to ask Iraq's Sunni neighbors to show solidarity with Baghdad.
Meanwhile the Saudi ambassador in London, Prince Mohammed bin Nawaf, rejected suggestions that his government was supporting or funding IS.
"It is the lack of international involvement that has paved the way for terrorist-affiliated movements to breed within Syria, and now Iraq," he said in a statement.
"We have previously urged the international community to take an in-depth look at the financial backing and organisational structure of this terrorist organisation.
"Had this been carried out it would have been revealed that rather than being the instigator of such terrorist network, Saudi Arabia is in fact the main target."