Thousands of foreign jihadists are still flooding into Syria to fight, US President Barack Obama warned Monday, as he urged greater efforts to halt the flow, particularly through the porous Turkish border.
"Not all of that is preventable, but a lot of it is preventable if we've got better cooperation, better coordination, better intelligence, if we are monitoring what's happening at the Turkish-Syria border more effectively," said Obama after meeting Iraqi Prime Minister Haider al-Abadi on the sidelines of the G7 summit in Germany.
The United States is leading a coalition aimed at eliminating Islamic State jihadists in Iraq that has unleashed 4,000 air strikes on IS positions, helping Baghdad to drive the jihadists out of some of their strongholds.
The militants launched a lightning offensive a year ago and quickly snatched over a third of Iraq's territory, declaring a "caliphate" with parts of Syria they also control.
They still hold much of western Iraq and have in recent weeks proven capable of snatching new territory.
Obama said that cutting off the flow of foreign fighters would "isolate and wear out (IS) forces that are already there because we're taking a lot of them off the battlefield.
"But if they're being replenished, then it doesn't solve the problem over the long term," he said.
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"This is an area where we've been seeking deeper cooperation with Turkish authorities who recognise it's a problem, but haven't fully ramped up the capacity they need, and this is something that I think we've got to spend a lot of time on," said Obama.
The president said another key issue was that some of the Iraqi forces were simply not battle ready.
"So we want to get more Iraqi security forces trained, fresh, well equipped, and focused, and Prime Minister Abadi wants the same thing," said Obama.
However, Obama said the Iraqi side needed to make commitments on "how recruitment takes place, how that training takes place".
"One of the things we're still seeing is, in (some places in Iraq) we've got more training capacity than we have recruits," he said, reiterating a coalition push for the Shiite leadership to tap the Sunnis.
Ancient sectarian tensions between the Shiite and Sunni sects of Islam run deep in Iraq.
The coalition has pushed for Sunni tribal fighters to be trained to fight the largely Sunni IS fighters in their own areas, but Shiite-ruled Baghdad is reticent to arm a population it fears may turn on it.