President Obama is expected to announce Monday the approval of up to 250 additional military personnel to support local forces inside war-ravaged Syria battling the Islamic State of Iraq and Syria (ISIS,) a senior administration official confirmed to CBS News.

The president will make the announcement Monday in remarks at the Hanover Messe fairgrounds in Germany as part of his farewell tour of Europe, reports CBS News correspondent Margaret Brennan.

In December, President Obama admitted publicly for the first time that a small contingent of 50 or so elite U.S. commandos has begun working inside Syria to "tighten the squeeze" on ISIS.

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Mr. Obama had made the announcement of the pre-planned incursion of 50 troops in a speech intended to prove his administration is stepping up the fight against the extremist group.

CBS News correspondent Charlie D'Agata met one of the groups American military personnel are working with inside northern Syria -- the Syrian Democratic Force. It is a newly-formed group made up largely of Kurdish and Arab fighters.

A local commander told D'Agata he had met with U.S. forces on the ground in Syria who are helping to coordinate local militias, and providing equipment, intelligence and training. The commander said in addition to helping call in accurate airstrikes, the deployment symbolically shows that the U.S. is committed to the fight.

In neighboring Iraq, the Obama administration has also been incrementally increasing the American military presence in the fight against ISIS.

Last week, Defense Secretary Ash Carter said the U.S. will send 200 more troops and a number of Apache helicopters to Iraq to assist in the fight to retake Mosul, Iraq's second-largest city that is currently under ISIS control.

The decision reflect weeks of discussions with commanders and Iraqi leaders, and a decision by President Barack Obama to increase the authorized troop level in Iraq by 217 - or from 3,870 to 4,087.

Most of the additional troops would probably be Army special forces, who have been used to advise and assist the Iraqis. The remainder would include some trainers, security forces for the advisers, and more maintenance teams for the Apaches.