Obama to discuss Islamic State with European leaders
Mr Obama told foreign military chiefs on Tuesday to expect a long campaign against the jihadist group, which controls large parts of Syria and Iraq.
He also expressed deep concern about the IS offensive on the town of Kobane, on Syria's border with Turkey.
US-led forces carried out 18 air strikes on IS targets near the town on Tuesday and Wednesday, the US said.
Central Command said in a statement that combat positions were destroyed and 16 buildings hit in the strikes, aimed at supporting Kurdish fighters who have been under siege in Kobane for almost a month.
The coalition has stepped up strikes in the region in recent days, in an effort to prevent IS from capturing the strategically important town.
The BBC's Kasra Naji, on the border near Kobane, says there is an air of optimism among the Kurdish militia, and a belief that they could drive IS out of the town in a few days.
Our correspondent says coalition aircraft now appeared to be targeting a single location, suggesting that this is probably the last neighbourhood in the town held by IS after its strength was degraded by heavy strikes on Tuesday.
Five more strikes were carried out against IS militants in Iraq - four near Bayji and one near Haditha Dam, US Central Command said.
Meanwhile the jihadists are said to be advancing on the Iraqi town of Amariya al-Falluja, one of the last still controlled by government forces in Anbar province and only 40km (25 miles) from the capital Baghdad.
'No quick fixes'
As the fighting and air strikes continued, the US military announced that it had named the operation against IS "Inherent Resolve".
Mr Obama told a meeting of senior military commanders from more than 20 Western and Arab countries at Andrews Air Force Base near Washington on Tuesday that air strikes would continue in both Kobane and Anbar province.
Mr Obama warned that they were facing a "long-term campaign".
"There are not quick fixes involved. We're still at the early stages."
"As with any military effort, there will be days of progress and there are going to be periods of setback," he added.
The battle for Kobane is regarded as a major test of whether the coalition's air campaign can push back IS in Syria.
US-led forces have been carrying out air strikes in support of Kurdish forces there for two weeks.
Jihadist militants are believed to control about half of the predominantly Kurdish town, from which more than 160,000 people have fled.
BBC
