One of Trump's directives will order the Joint Chiefs to submit a strategy within 30 days to defeat Islamic State terrorist groups, a senior administration official said, signaling that the new president hopes to make good on his campaign promise to more aggressively confront global terrorism than his predecessor.
Yet, many in the USA military are wary of Russia's role in Syria, with Moscow seen as seeking first and foremost to support and defend President Bashar al-Assad's regime.
Last week, General Joe Dunford, chairman of the Joint Chiefs of Staff, said he would present Mattis with options to "accelerate the campaign" against IS.
Another option that could be presented is to send more U.S. troops into Syria to engage in combat [.] to help push ISIS fighters out.
"This is evil. This is a level of evil that we haven't seen".
What also remains to be seen is whether the dual bans instituted by both the USA and Iraq will have an impact on the relationships and cooperation on the ground in the fight against ISIS there.
In a call with Russian President Vladimir Putin Saturday, Trump and his counterpart agreed to increase cooperation between the two countries' militaries in the fight against ISIS, the Kremlin said in a statement.
Donald Trump says Mexico has taken advantage of US
Trump views the wall, a major part of his election campaign, as part of a package of measures to curb illegal immigration. The move prompted Mexico's current leader, Enrique Pena Nieto, to cancel his scheduled trip next week to Washington .
Across the border in Iraq, local forces backed by US -led coalition airstrikes and advisers on the ground have secured a major part of Islamic State's Iraqi stronghold of Mosul.
The slow, steady assault has driven ISIS fighters out of part of the city on the east bank of the Tigris River, and forces are now preparing an assault on ISIS-held Mosul neighbourhoods on the west bank.
According to reports, an escalation of the U.S. role could involve more USA armor and helicopters involved in the assaults on ISIS positions together with Iraqi, Turkish and Kurdish forces.
Mr Trump "could elect to put American boots on the ground in larger numbers", said Lt-Gen Barno. "That all entails new uses of military power. and that opens the prospect of a deeper involvement with more casualties".
Mr. Trump vowed to defeat ISIS during the campaign. We support combat operations against ISIS and al Qaeda from ports and airbases in eleven other Muslim countries.
One noticeable, if cosmetic, change: Trump referred to the group as ISIS, the Islamic State of Iraq and Syria, and not ISIL, the Obama administration's preferred acronym for the group, which stands for the Islamic State of Iraq and the Levant.
Mr Trump signed a flurry of executive actions into effect in his first full week in office.