Obama highlights progress against Islamic State militants

US President Barack Obama  on Thursday touted progress the US and its allies have made in the military campaign against the Islamic State (IS) group while adding that it still posed a threat to the West.

At a press briefing he addressed a wide range of security topics, including the fight against Russia's involvement in Syria and $400m shipped to Iran after the nuclear deal.

Obama said the IS militant group still has the ability to direct and to inspire attacks.

"We're going to keep going after ISIL aggressively across every front of this campaign," Obama said, using an acronym for IS.

While the US-led air and ground campaign against the group's strongholds in Iraq and Syria have cost it territory, IS is adapting by reverting to high-profile attacks and by using the internet to recruit members and train them and by encouraging "lone wolf" attacks. IS also maintains control of a few cities, including Mosul in Iraq and Raqqa in Syria.

"In the meantime, though, you're seeing ISIL carry out external terrorist acts and they've adopted from al-Qaeda," he said.

Speaking to reporters after his meeting with security and military officials, Obama acknowledged that pressure against the group has prompted the militants to increase attacks outside Syria and Iraq, including in the US, France and Turkey.

"As we have seen, it is difficult to prevent small cells of terrorists willing to kill the innocent and [who] are willing to die," he said.

Russia, war in Syria

The Syrian government continues to violate a truce in the war there, and Russia's actions in Syria raise questions about its intentions in the country, Obama said.

"The US remains prepared to work with Russia to try to reduce the violence and strengthen our efforts against ISIL and al-Qaeda in Syria. But Russia has failed to take the necessary steps. Given the deteriorating situation, it is time for Russia to show it is serious about pursuing these objectives," Obama said.

In the same speech, Obama pushed back against criticism that the administration's payment of $400m in cash to Iran amounted to ransom in exchange for the release of American prisoners.

"We announced these payments in January, many months ago. It wasn't a secret. This wasn't some nefarious deal," Obama said.

He said the US does not pay ransom for hostages and that the money was not linked to the prisoners' release.

"The reason that we had to give cash is precisely because we are so strict in maintaining sanctions and we do not have a banking relationship with Iran," Obama said. "It is not at all clear to me why it is that cash as opposed to a cheque or a wire transfer has made this into a news story."