US secretary of state John Kerry has said that neither the United States nor the rest of the world will stand by and watch the Islamic State militant group spread its evil.
Mr Kerry was in Baghdad to meet with Iraq's new leaders and pledge US support for eliminating the extremist group and the threat it poses.
He said President Barack Obama would later outline in specific detail what steps the US is prepared to take to defeat the Islamic State, which has overrun parts of northern Iraq and Syria.
Mr Kerry did not reveal Mr Obama's plans. But he predicted a coalition of at least 40 nations ultimately will eliminate the Islamic State.
With a new Iraqi government finally in place and a growing Middle East consensus on defeating insurgent threats, Mr Kerry pressed Iraq's Shia leader to quickly deliver more power to wary Sunnis - or jeopardise any hope of defeating the Islamic State group.
Mr Kerry landed in the Iraqi capital just two days after newly sworn in prime minister Haider Abadi seated his top government ministers, a crucial step towards restoring stability in a nation where security has spiralled out of control since the beginning of the year. As Mr Kerry and Mr Abadi were meeting, two car bombs exploded simultaneously in the south-eastern neighbourhood of New Baghdad, killing 13 people.
The trip marks the first high-level US meeting with Mr Abadi since he became prime minister, and it aimed to symbolise the Obama administration's support for Iraq nearly three years after US troops left the war-torn country. But it also signalled to Mr Abadi, a Shia Muslim, that the US was watching to make sure he gives Iraqi Sunnis more control over their local power structures and security forces, as promised.
Mr Abadi's predecessor, former prime minister Nouri al-Maliki, for years shut Sunnis out of power and refused to pay tribal militias salaries or give them government jobs - and in turn sowed widespread resentment that Islamic State extremists seized on as a recruiting tool.
Mr Abadi hosted Mr Kerry in the ornate presidential palace where Saddam Hussein once held court, and which the US and coalition officials later used as office space in the years immediately following the 2003 invasion of Iraq. In brief remarks following their meeting, Mr Abadi noted that Iraq's violence is largely a spillover from the neighbouring civil war in Syria, where the Islamic State militants have a safe haven.
"Of course, our role is to defend our country, but the international community is responsible to protect Iraq, and protect the whole region," Mr Abadi said, speaking in English. "What is happening in Syria is coming across to Iraq. We cannot cross that border - it is an international border. But there is a role for the international community and for the United Nations ... and for the United States to act immediately to stop this threat."
Mr Kerry praised the new Iraqi leadership for what he described as its "boldness" in quickly forming a new government and promising to embrace political reforms that would give more authority to Sunnis and resolve a longstanding oil dispute between Baghdad and the semi-autonomous Kurdish government in the nation's north.
"We're very encouraged," Mr Kerry said. He assured Mr Abadi that Mr Obama will outline plans later "of exactly what the United States is prepared to do, together with many other countries in a broad coalition, in order to take on this terrorist structure, which is unacceptable by any standard anywhere in the world ".
Mr Kerry also met with new Iraqi parliament speaker Salim al-Jabouri, one of the country's highest-ranking Sunnis, who expressed hope that Iraq will overcome terror threats and establish a vital democracy - two issues that have dogged the nation for years.
"We are before a very critical and sensitive period in the history of Iraq," Mr Jabouri told Mr Kerry.
Mr Kerry's trip comes on the eve of a meeting in Jeddah, Saudi Arabia, where he and Arab leaders across the Middle East will discuss what nations can contribute to an ever-growing global coalition against the Islamic State. The US and nine other countries - Canada, Australia and across Europe - agreed last week to create a united front against the mostly Sunni extremist group that has overrun much of northern Iraq and Syria. Thursday's meeting in Jeddah seeks to do much of the same and will gauge the level of support from the Sunni-dominated Middle East region. Mr Kerry is also to visit Jordan.
Meanwhile, in Paris, French government spokesman Stephane Le Foll said all five permanent members of the UN Security Council - the US, the UK, France, Russia and China - would take part in a conference in the French capital on Monday that will focus on stabilising Iraq. During a French cabinet meeting, foreign minister Laurent Fabius brought up the issue of whether Iran would be invited to the Paris conference, but it "has not yet been decided", according to Mr Le Foll.
The US has already launched about 150 air strikes on Islamic State militants in Iraq over the past month, a mission undertaken at the invitation of the Iraqi government and without formal authorisation from Congress. And it has sent military advisers, supplies and humanitarian aid to help Iraqi national troops and Kurdish forces beat back the insurgents. It was not clear what, if any, military action Mr Obama would be willing to take in Syria, where he has resisted any mission that might inadvertently help president Bashar Assad and his government in Damascus, which has so far survived a bloody three-year war against Sunni rebels. Mr Obama has ruled out putting US combat troops on the ground.
France's foreign minister said his country is ready to take part in air strikes against extremist fighters in Iraq if needed.
Laurent Fabius called for international mobilisation against "this transnational danger that could reach all the way to our soil".
France has said it would join a US-led coalition and is sending arms to Kurdish authorities to fight the militants.
The French president and foreign minister are going to Iraq on Friday and hosting an international conference on Monday on how to stop the group and help Iraq.
Mr Fabius said in a speech in Paris that "we will participate, if necessary, in military air action".