President Barack Obama will announce later on Monday plans to send up to 250 additional U.S. special forces troops to Syria to support local Syrian forces fighting against Islamic State, a White House adviser said.

The deployment will increase U.S. forces in Syria to about 300. Its goal is to accelerate recent gains against Islamic State and appears to reflect growing confidence in the ability of U.S.-backed forces inside Syria and Iraq to claw back territory from the hardline Sunni Islamist group.

“We’ve seen across parts of northern and eastern Syria progress as ISIL has been pushed out of some strongholds,” Deputy National Security Adviser Ben Rhodes told reporters in the northern German city of Hanover, the last stop on Obama’s six-day foreign tour.

“We want to accelerate that progress and we believe the commitment of additional U.S. special forces can play a critical role.”

Obama will explain his decision in a speech at 11:25 a.m. (0925 GMT) in Hanover, where he discussed the Syria crisis with German Chancellor Angela Merkel on Sunday. Obama and Merkel are due to hold talks with the leaders of Britain, France and Italy in the afternoon.

Islamic State, also known as ISIS or ISIL, controls the cities of Mosul in Iraq and Raqqa in Syria and is proving a potent threat abroad, claiming responsibility for major attacks in Paris in November and Brussels in March.

Rhodes emphasised that the U.S. troops would not themselves be directly involved in combat, but would act as support for Syrian forces on the ground.

“The mission that they are being given is not to go into Syria and engage the enemy, to engage ISIL,” he said. “They are not being sent there on a combat mission. They’re being sent there on a mission to be advising and assisting and supporting the forces that are fighting ISIL on the ground.”

While Obama has resisted putting U.S. troops into Syria, where a five-year civil war has killed at least 250,000 people, he sent 50 U.S. special operations forces to Syria last year in what U.S. officials described as a “counterterrorism” mission rather than an effort to tip the scales in the war.

Obama pledged to wind down wars in the Middle East when he was first elected in 2008. But in the latter part of his presidency he has found it necessary to keep or add troops to help with conflicts in Iraq, Syria and Afghanistan.

The president’s international trip began in Riyadh, where he held talks with Gulf Arab monarchs concerned that Washington’s commitment to the Middle East had diminished. He also spent three days in Britain before arriving in Germany on Sunday.

 ‘WE HAVE MOMENTUM’

Obama has said the U.S.-led coalition fighting Islamic State had made key gains in squeeze the group’s territory in Iraq and Syria, reducing its numbers and cutting off its finances.

“We have momentum, and we intend to keep that momentum,” he said earlier this month.

In Iraq, the group has been pulling back since December when it lost Ramadi, the capital of the western province of Anbar. In Syria, the jihadist fighters have been pushed from the strategic city of Palmyra by Russian-backed Syrian government forces.

The Pentagon also announced last week that about 200 more troops would be deployed to Iraq, mainly to advise Iraqi troops fighting Islamic State.

Since U.S.-backed forces recaptured the strategic Syrian town of al-Shadadi in late February, a growing number of Arab fighters in Syria have offered to join the fight against the group, U.S. officials told Reuters in early April.

Syria dominated the Sunday talks between Obama and Merkel. The German leader had just returned from a trip to Turkey to see refugee camps along the border.

The European Union has grappled with the flood of about a million migrants last year, most fleeing the Syria crisis. Merkel pushed her EU partners to accept refugees, and recently hammered out a deal with Turkey to stop the migrant flow.

After meeting with Merkel for about 90 minutes, Obama told reporters he was “deeply concerned” about a surge in violence in Syria, where government forces have stepped up bombing of rebel-held areas around the strategic city of Aleppo.