U.S. Secretary of State John Kerry on Thursday, January 21 said the Islamic State group would be "very seriously" weakened in Syria and Iraq this year, AFP reports.

Air strikes by the alliance that includes Gulf states, France and Britain have been pounding IS positions since August 2014, with Washington claiming major gains against the extremists.

"I think that by the end of 2016, our goal of very seriously denting Daesh in Iraq and Syria and of trying to have an impact on Mosul (in Iraq) and Raqa (in Syria) will be achieved," Kerry told reporters on the sidelines of the World Economic Forum in Davos, using an alternative name for IS.

"We are on track, we are doing serious damage to Daesh today," he said, according to AFP.

The Pentagon estimates that IS has lost 20-30 percent of the total territory they were in control of in Iraq and Syria, including up to 40 percent in Iraq alone.

Kerry said he would meet the foreign ministers of 24 coalition nations in Rome on February 2 to discuss strategy and possible "additional commitments".

The U.S, has called on allies to contribute special forces as a key part of the efforts to bolster coalition forces fighting the jihadist group.