President Barack Obama welcomed Iraq's Prime Minister Nuri al-Maliki to the White House on Friday, as sectarian violence in the country hits its deadliest peak since April 2008.

The Oval Office talks took place nearly two years after the last American troops left Iraq following an eight-year occupation and as a wave of Al-Qaeda attacks sows terror in the Iraqi Shiite community.

The violence is stirring fears the country may slide into an abyss exacerbated by the brutal war rending Syria next door.

October was Iraq's deadliest month since April 2008, with 964 killed and another 1,600 wounded, according to data from the Iraqi ministries of health, interior and defense.

The vast majority of those killed were civilians.

"The security situation is not only bad... it not only could reverse all of the gains of 2008, it could tear the country apart if both Maliki and the United States do not act quickly," said James Jeffrey, who was until last year the US ambassador to Iraq.

General David Petraeus, who led the troop surge credited by some with quelling the last sectarian explosion in Iraq, warned in a Foreign Policy article that the situation was now so dire that the past sacrifices of US troops could be squandered.

Maliki, blamed by some Iraq watchers in Washington for marginalizing Sunnis and for sinking a well of sectarian anger for extremists to exploit, is blunt about the challenge.

"The terrorists found a second chance," he said Thursday in Washington, warning that Al-Qaeda and allied groups were a "virus."

Maliki has a wish list of US military hardware, including attack helicopters to go with already ordered fighter jets to help his ill-equipped military battle insurgents.

There is a certain irony in his request, given the failure of Iraqi and US negotiators to agree legal immunity for US troops that would have allowed a residual American force to stay behind in Iraq.

Iraq's slide back into violence has revived questions here about the wisdom of the complete US withdrawal, the Maliki government's conduct since and America's future relationship with a nation it invaded in 2003 to topple Saddam Hussein.

Could a prolonged US presence have quelled the Al-Qaeda resurgence? Or was a sectarian breakdown inevitable, given Iraq's restive neighborhood, fractured ethnic make-up and tortured domestic politics?

The Iraq of November 1, 2013 bears little resemblance to the picture Obama painted two years ago when troops came home, when he hailed the "extraordinary" US achievement.

"We are leaving behind a sovereign, stable and self-reliant Iraq," Obama said.

The idea that Obama "ended" the Iraq war -- which he once branded "dumb" and built a political career on opposing -- underpinned his re-election campaign last year.

"Four years ago, I promised to end the war in Iraq. We did," he said at his renominating convention.

But when US troops left, the war went on.

Obama's critics accuse the president of throwing away hard-won gains by leaving Iraq prematurely and some also round on Maliki accusing him of opening sectarian divisions.

"I urge President Obama to make clear to the Prime Minister that the United States is concerned about these developments and that the solution to Iraq's problems lies not in a closer alliance with Tehran, but in bridging divides within Iraq and reinvigoration of the US-Iraqi partnership," said Republican Senator Marco Rubio.

Obama had public support in leaving a war many Americans saw as a quagmire and may have spared American forces from again being stuck in the crossfire of sectarian strife.

Senior US officials do believe some progress has been made -- approving of Maliki's recent visit to Anbar province and pointing to scheduled national elections in Iraq early next year.

They also privately note that so far, there has been little resurgence of attacks by Shiite militias in reprisal for activity by the Islamic State of Iraq and the Levant, the front group for Al-Qaeda.

Washington is also increasing intelligence cooperation with the Iraqi government as it battles radicals.

"We really want to help the Iraqis have a better vision of what they face so they can target it effectively," a senior official said, though declining to get into intelligence information.

Maliki is having to make his case for US military hardware amid skepticism in Congress of his performance.

"Unfortunately, Prime Minister Maliki's mismanagement of Iraqi politics is contributing to the recent surge of violence," wrote a bipartisan group of senators wrote in a letter to Obama this week.

The senators want more cooperation from Maliki in curtailing arms supply flights from Iran to the Assad regime in Syria over Iraqi air space, and worry about Tehran's influence in Baghdad.