U.S. Secretary of State John Kerry says the Obama administration decided to airdrop weapons and ammunitions to "valiant" Kurds fighting Islamic State extremists in the Syrian border town of Kobani because it would be "irresponsible" and "morally very difficult" not to support them.

Speaking in the Indonesian capital on Monday, Kerry told reporters that the administration understood ally Turkey's concerns about supplying the Kurds, who are linked to a Kurdish group that Ankara fiercely opposes.

But, he says the situation is such in the besieged town of Kobani that the resupplies were deemed absolutely necessary in a "crisis moment."

Kerry says the airdrops are intended to be temporary and that the U.S. has asked Turkey to allow Kurdish fighters from Iraq into Kobani to help.