Iraq’s new broad-based government will be the “engine” of the Obama administration’s plan to turn back the rapid advances of Islamic State militants, Secretary of State John F. Kerry said Wednesday. But lined with familiar faces, the much-vaunted governing coalition faces huge challenges in playing that role.

Kerry made an unannounced visit to the Iraqi capital just hours before President Obama, in a televised speech, detailed a multi-pronged strategy that includes building a “broad coalition” against the Islamic State and carrying out airstrikes in Syria. Kerry announced $48 million in new humanitarian aid and promised unspecified additional support for Iraq’s planned national guard forces and its military campaign against the militants.

The United States had tied an increase in military assistance to Iraq to the formation of a new government incorporating the country’s estranged Sunni and Kurdish minorities. On Wednesday, Kerry congratulated Iraqi officials for achieving that — after months of political wrangling.

Analysts, however, say the cabinet’s lineup, which includes a slew of former ministers, represents little break from the past.

“Much of the praise for this new government is unwarranted and premature,” said Wayne White, a policy expert at the Washington-based Middle East Institute and a former State Department analyst. “Most of its cabinet members are retreads from previous sectarian governments.”

Already the cracks are showing, with the Kurds announcing that they would join the government for only a three-month trial period. The security portfolios also have been left empty, after Shiite politicians objected to the Sunni candidate for defense minister and Sunnis opposed the Shiite pick for interior minister. Four other posts are yet to be filled.

But Iraqi officials say there is a new air of optimism under the leadership of Prime Minister Haider al-Abadi, who formally took power Monday, and an awareness of the crisis at hand.

“The spirit of the government and its mentality is different,” said Salim al-Jubouri, the speaker of parliament, after he met with Kerry. “The personality of the prime minister is different.”

For the United States, it appears to be different enough. The Obama administration is relieved that Abadi edged out longtime leader Nouri al-Maliki, and the new prime minister has pledged to govern with genuine inclusivity, which had been missing under Maliki.

“Now that the Iraqi parliament has approved a new cabinet with new leaders and representatives from all Iraqi communities, it’s full speed ahead,” Kerry said.

“A new, inclusive Iraqi government has to be the engine of our global strategy against ISIL,” he added, using an alternative acronym for the Islamic State, a Sunni militant group that has proclaimed a caliphate on a third of Syrian and Iraqi territory.

A key challenge for the new government will be to enlist Sunnis in the fight against the Islamic State. When the militants swept in and seized the northern city of Mosul in June, many residents welcomed them, deeply dissatisfied with what was seen as a deeply sectarian government in Baghdad.

The new Iraqi national guard, modeled on the Sunni Awakening movement that had battled al-Qaeda alongside U.S. troops, is a cornerstone of Abadi’s mobilization strategy.

Washington is encouraged by Abadi’s plan to loosen the Shiite-led Baghdad government’s hold on security matters, long an irritant in Sunni areas. Some expanded international help for the new government is expected to further his plan to establish a national guard that answers to provincial governors.

But for his strategy to work, Abadi, a Shiite, will have to co-opt Sunni leaders who remain doubtful about his leadership.

In a meeting with Kerry, Abadi warned that the threat from the Islamic State is growing.

The group is “mobilizing an international network,” drawing funding and foreign fighters to its cause, Abadi said after the meeting.

“We are fighting these people,” he said. “They are a challenge to the whole region, to the international community.

“This cancer is threatening the whole region, and we have the resolution to fight,” he continued, appealing for more and immediate international help.

Abadi told Kerry that Iraq’s ability to fight the militants is limited because its forces cannot cross the border into Syria. Others must do that job, he said, though he did not specifically call for U.S. airstrikes on Syria.

The Obama administration is expected to launch such assaults later but is focused first on stopping the militant march in Iraq.

Syria has said that it would consider any U.S. military action inside its borders to be a hostile act.

Iraq was Kerry’s first stop on a recruitment tour of Arab and European nations to amass financial, political and military support for a long fight against the Islamic State. The U.S. plan relies on that broader base of support as a firmer foundation for Iraq to combat the militants.

Jubouri, a Sunni, said Kerry had asked him to lead efforts to reach out to potential Sunni Arab partners in the Persian Gulf region.

“The visit comes under circumstances in which there are real opportunities,” a senior State Department official said, citing “a real shake-up in the cabinet” and a chance for progress on key issues that have bedeviled Iraqi leaders for eight years.

The official added that the Obama administration is not naive about the challenges for Abadi or the coalition supporting him.

“This is going to be extremely, extremely difficult. The problems that are confronting Iraq are incredibly challenging,” the official said.