President Barack Obama is said to be ready to tell Americans on Wednesday that he is prepared to expand air strikes on the Islamic State into Syria, as he steels them for a long fight against the jihadists.
Despite devoting much of his presidency to exiting Middle Eastern entanglements and avoiding new ones, Obama is poised to move the campaign against the so-called Islamic State, which has already seen air strikes in Iraq, into a more offensive phase.
"You will hear from the President how the United States will pursue a comprehensive strategy to degrade and ultimately destroy ISIL," a senior official said on condition of anonymity.
The plan will include US military action against Islamic State forces and new support for the opposition in Syria and the new "inclusive" government in Iraq, the official said.
"The President will discuss how we are building a coalition of allies and partners in the region and in the broader international community to support our efforts, and will talk about how we work with the Congress as a partner in these efforts."
The New York Times reported, without giving further details, that Obama was ready to authorize air strikes against IS strongholds in Syria -- a step he has so far been unwilling to take.
The White House, loath to steal Obama's thunder in big speeches, would not confirm the report, but lent it credibility by not denying it.
Mindful of avoiding what he believes are the mistakes of the last decade, Obama will assure millions of television viewers at 9pm (0100 GMT Thursday) that he will not send conventional ground troops back to Iraq to fight a group that has beheaded two US journalists.
The speech will also lack a definitive timeline for US operations against IS, after several reports cited senior officials as saying they could outlast Obama's presidency, which ends in January 2017.
"I think the American people need to expect that this is something that will require a sustained commitment," said White House spokesman Josh Earnest.
The address will come at a poignant time -- on the eve of the 13th anniversary of the September 11 attacks, when Islamic radicalism on a mass scale scorched the US homeland for the first time, and drew America into exhausting overseas wars and a still unending anti-terror campaign.
Earnest said Obama would "talk about the risks that the United States faces, and he'll talk about the strategy that he has put together to confront those risks, to mitigate them, and ultimately to degrade and destroy ISIL," he said, using an alternative acronym for IS.
- Cautious hope -
White House aides say the new strategy will be anchored on the cautious hope that Iraq's new unity government will prove more inclusive than ex-prime minister Nuri al-Maliki who was blamed for fanning the sectarianism that eased Islamic State's rise.
The president briefed senior congressional leaders on his plan on Tuesday, and an aide to House Speaker John Boehner stirred speculation that he could order US troops back to Iraq on a mission strictly limited to training their Iraqi counterparts and to call in air strikes against IS forces.
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"The speaker stated he would support the president if he chose to deploy the military to help train and play an advisory role for the Iraqi security forces and assist with the lethal targeting of ISIL leadership," the aide said.
There was no comment from the White House on whether Obama was considering such an idea, after aborting plans for a small contingent of American soldiers to stay on in Iraq after 2011, following a disagreement with the Maliki government.
Obama, who sees ending wars in Afghanistan and Iraq as a centerpiece of his legacy, is also under pressure to announce stepped-up support for moderate rebels of the Free Syrian Army, despite his antipathy to intervening in Syria's vicious civil war.
Washington wants to ensure that President Bashar al-Assad, who it regards as a war criminal, does not benefit from any power vacuum left in the event that US military action degrades IS.
A White House official said Obama told congressional leaders on Tuesday that he did not need fresh permission for military action he is planning to take against IS, a question that has divided senior lawmakers.
- Rebel aid -
A senior US official, however, told AFP that Obama told the bipartisan leadership of the House and the Senate that he did need lawmakers to vote on intensifying US training and equipping of moderate Syrian rebels.
Obama previously asked $500 million of funding in May and June, and wants action on the request before Congress leaves town within weeks, ahead of midterm elections in November.
The speech will represent a chance for Obama to redress criticism that he has been slow to respond to IS, amid fears fighters armed with Western passports could hit US targets.
The president started the work of creating an international coalition to take on IS at the NATO summit last week.
Defense Secretary Chuck Hagel has been in the Middle East. Secretary of State John Kerry arrived in the region Wednesday and will also visit Saudi Arabia to accelerate Washington's efforts
Public opinion in the United States meanwhile appears to be shifting in favor of a limited intervention in Syria.
A Wall Street Journal/NBC News poll published Tuesday found two-thirds of those asked favored taking on IS.