RNA - The former Republican House Speaker, who informally advises Trump, said he did “not think they had a strategy” but was confident that “they know, which is important, is that they are gonna need a strategy”.
Despite this, Mr Gingrich told Fox News he was confident that Mr Trump’s security advisory team - which includes several retired generals - would come up with an “aggressive” action plan.
He said: “They are going to be able to produce a very aggressive strategy. They have a much better grip on reality than the Obama administration did”.
This is a markedly different tone from the confident bluster of the campaign trail where Mr Trump said Isis' “days are numbered” but refused to divulge his plan for fear of the terror group hearing about it.
In April, the former reality star said: “If I am elected President, Isis will be gone and they will be gone quickly. Very, very quickly.
“I won’t tell them where and I won’t tell them how. We must as a nation be more unpredictable.
“Containing the spread of radical Islam must be a major foreign policy goal of the United States and indeed the world.”
Mr Gingrich said one of the ways Mr Trump could fight back against extremism would be to suspend civil liberties - which he claims Abraham Lincoln did during to the American Civil War.
He said: “People should go back and look at how Lincoln dealt with Southern sympathisers during the Civil War.
“We passed a Sedition Act for example, which changed our ability to control people who were advocating treason.”
Historians say Lincoln did not pass a specific law tackling dissent but he did suspend several First Amendment freedoms such as Habeas Corpus - the right to a speedy trial.
Mr Gingrich’s suggestion comes as it emerged Mr Trump was still keen to establish a “registry” of all 3.3m Muslim people in the US because the Berlin terror attack proved he was “100 per cent correct”.
Following his victory in the Electoral College last month, the Muslim registry was one of several outlandish pledges - including the infamous wall on the Mexican border - he appeared to have backtracked on.
But after an attack where Anis Amri ploughed a stolen lorry into the crowd at a Christmas market in west Berlin, killing 12 people, Mr Trump renewed his registry pledge saying: “It’s an attack on humanity and it’s got to be stopped”.
It is still unclear how Mr Trump will be able to put this idea into practice without violating the US Constitution but the Council on American-Islamic Relations reported at least 900 hate crime incidents against Muslims in the weeks after the election.
These have included everything from mosques being vandalised and set on fire to Muslims being beaten, shot and stabbed in the street.
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