President Barack Obama has authorised surveillance flights over Syria in order to gather intelligence on the Islamic State group, a senior US administration official said.
Tuesday’s move could mark the first step towards US air strikes against targets inside Syria.
The official, who spoke to the AP news agency, was not authorised to discuss Obama's decision by name and spoke only on condition of anonymity.
The White House said Obama has not yet made a decision on whether to take military action inside Syria.
The US is already launching air strikes against Islamic State targets in Iraq. The group announced last week that it had murdered an American journalist in Syria and was threatening more US hostages.
The Reuters news agency had earlier reported that Washington was planning to send surveillance aircraft, including unmanned drones, to gain a clearer picture of the Islamic State fighters, who have seized territory in both Syria and Iraq.
The Wall Street Journal said that US Central Command, which oversees American forces in the Middle East, had asked for additional surveillance planes to be used in Syria.
The surveillance planes would provide information in addition to that already collected by US satellites and informants, the journal said.
Joshua Landis, a prominent analyst on Syria, told Al Jazeera that advisers to Obama had been telling the president that the US would only be able to uproot the Islamic State group if they get involved in Syria.
But the dilemma Obama was facing was the lack of partners in Syria, Landis said. Neither the Syrian regime, nor the fragmented moderate rebels could be seen as reliable allies.
Landisk, who is the director of the centre for Middle East Studies at the University of Oklahoma, said that Obama must be clear about what he intends to do in the long-term.
US officials, according to Reuters, have said privately that Washington has no plans to seek consent from the Damascus regime for any military flights.
The Syrian government on Monday warned that Syria must be involved in co-ordinating any air strikes against the Islamic State group in Syria.
In a news conference in Damascus, Foreign Minister Walid al- Muallem said his country was ready to work with the international community- including its rivals, the US and UK, - to battle against "terrorists".
"Syria is ready for co-operation and co-ordination at the regional and international level to fight terrorism and implement UN Security Council resolution 2170," Muallem said.
The UN Security Council passed a rare unanimous resolution on August 15 intended to weaken armed groups in Iraq and Syria by choking off their funding and stemming the flow of foreign fighters.
The resolution targeted both the Islamic State group and al-Nusra Front, which is al-Qaeda's Syrian affiliate.
Syria's government considers not only these two groups, but all those fighting to overthrow President Bashar al-Assad to be "terrorists".