US President Donald Trump is expected to order up a new plan for defeating the Islamic State (IS) militants with expanded US military involvement as he makes his first visit to the Pentagon Friday.

Trump, who pledged to eradicate the extremist group during the presidential campaign, is reportedly preparing to direct new Defense Secretary James Mattis to more aggressively attack IS positions with the aim of defeating them more quickly.

That could mean more US forces and military hardware moving into Iraq and Syria, according to analysts.

"We have to get rid of ISIS. We have no choice," Trump told Fox News's Sean Hannity in an interview broadcast Thursday, using another acronym for the Islamist militant group.

"This is evil. This is a level of evil that we haven't seen."

After his predecessor Barack Obama took a longer term view of the anti-IS fight, with a more cautious commitment of US forces, "President Trump might be looking for something with quicker results, that could put some more options on the table," retired general David Barno told National Public Radio Friday.

The Wall Street Journal reported that Trump will give the Pentagon 30 days to come up with a new set of options for a tougher campaign against IS.

The United States currently has 5,000 troops in Iraq and 500 in Syria as "advisors" -- but also US artillery and aircraft to help in the fight.

They have provided substantial support to the assault led by Iraqi forces on IS's hold on the key city of Mosul.

The slow, steady assault has driven IS fighters out of the part of the city on the east bank of the Tigris River, and forces are now preparing an assault on IS-held Mosul neighborhoods on the river's west bank.

According to reports, an escalation of the US role could involve more US armor and helicopters involved in the assaults on IS positions together with Iraqi, Turkish and Kurdish forces.

Trump "could elect to put American boots on the ground on larger numbers," Barno said. "That all entails new uses of military power .... and that opens the prospect of a deeper involvement with more casualties."

Trump promised during his presidential campaign to eliminate IS saying he had a secret plan to quickly defeat the group.

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.

"What is really important is first that we have a conversation about what we are doing today, why we are doing it, and what other things might be done and why we haven't done it to date," Dunford told reporters in Brussels.

Trump is also open to conducting joint operations with Russia against the IS in Syria, his spokesman said earlier this week.

"If there's a way we can combat ISIS with any country, whether it's Russia or anyone else, and we have a shared national interest in that, sure, we'll take it," press secretary Sean Spicer told reporters.

During his Pentagon visit, Trump is expected to sign executive orders limiting the flow of refugees into the United States and setting up "extreme vetting" of some migrants, according to CNN.