Obama will explain his decision in a speech at 11:25 am (0925 GMT) in Hanover, where he discussed the Syria crisis with German Chancellor Angela Merkel on Sunday. They will meet with other major European leaders after his remarks, Reuters reported.
Daesh controls the cities of Mosul in Iraq and Raqqa in Syria and is proving a potent threat abroad, claiming credit for major attacks in Paris in November and Brussels in March.
While Obama has resisted putting US troops into Syria, where a five-year civil war has killed at least 250,000 people, he sent 50 US special operations forces to Syria last year in what US officials described as a "counterterrorism" mission rather than an effort to tip the scales in the war.
"He (Obama) intends to put in more ... forces to the tune of 250 in Syria," one US official said on Sunday, adding he was unable to break down how many of those would be special operations forces and how many might be medical or intelligence support personnel.
"The president has authorized a series of steps to increase support for our partners in the region, including Iraqi security forces as well as local Syrian forces who are taking the fight to ISIL," said a second Obama administration official.
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 is ending a six-day international trip that began in Riyadh, where he held talks with Persian Gulf Arab monarchs concerned that Washington's commitment to the Middle East had diminished.
After that meeting, Obama sidestepped a question about whether he would add special forces in Syria, saying: "None of the options are good" if political talks fail to end the civil war there.
The Pentagon also announced last week that about 200 more troops would be deployed to Iraq, mainly to advise Iraqi troops fighting Daesh.