Iraqi forces, backed by hundreds of U.S. military forces, have taken 800 square kilometers back from the Islamic State in Iraq and Syria (ISIS) in the first week of the Mosul offensive, U.S. officials said Monday.

That is on track with what was expected, said the officials, who spoke to reporters at the Pentagon on the condition of anonymity.

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Pentagon spokesman Navy Capt. Jeff Davis said Monday there was no question that Mosul would fall.

"Everything is in favor of the coalition here to defeat ISIL," Davis said, using another acronym for ISIS. "They are a much smaller and vastly inferior force."

Those assessments of the offensive, which began on Oct. 17, differ from the one offered by GOP presidential nominee Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE.

"The attack on Mosul is turning out to be a total disaster. We gave them months of notice. U.S. is looking so dumb," Trump tweeted Sunday evening, referring to giving ISIS fighters defending the city advance notice of the offensive.

Trump followed up that tweet in radio interviews on Monday, telling a New Hampshire radio station: "We give them 12 months notice that we're going to attack. They've built-up — and as you see, it's a very tough situation right now. They're using human shields, they've got all sorts of — you know, they're all dug in. They didn't know about it. Instead of doing a surprise attack, remember the old days? Surprise attack?"

"Our leaders are so incompetent," he said in the interview, according to NBC.

Earlier Monday, Trump told Pat Robertson on "The 700 Club" that the Iraqi forces retaking Mosul would fail.

Trump's comments came amid reports that ISIS was attempting to attack other Iraqi cities as a diversionary tactic, and was putting up tough resistance in cities surrounding Mosul.

Defense and military officials have long said they expected ISIS to put up a fight to hold on to their de facto capital in Iraq.

Officials have also said that they expect the fight to get tougher as Iraqi forces get closer to the city center, and that ISIS has been expecting and preparing for an offensive since it first took over the city.

ISIS seized Mosul in June 2014, when it stormed into Iraq from Syria in a lightning-quick offensive.

Trump has repeatedly slammed administration and military leaders for discussing the Mosul offensive in advance and called for a "sneak attack." Those remarks have remarks prompted new scorn from defense experts on both sides of the aisle.

Bill Kristol, editor of the conservative magazine Weekly Standard, tweeted, "Trump compresses an amazing amount of ignorance, idiocy & buffoonery into 140 characters. And does damage to the country at the same time."

Trump compresses an amazing amount of ignorance, idiocy & buffoonery into 140 characters. And does damage to the country at the same time. https://t.co/2CuEr0OSER — Bill Kristol (@BillKristol) October 24, 2016

Defense experts have said it would be impossible to conduct a "sneak attack" on Mosul, since it would be difficult to hide the 30,000 Iraqi and Kurdish peshmerga forces advancing towards the city.

They have also pointed out that Iraqi leaders themselves have long-discussed the offensive publicly. Experts also said announcing the start of the offensive also allows civilians trapped in the city to prepare, or flee if they can, or convince some ISIS fighters to run or put down their arms.

“There are over a million innocents in the city so you want to give them an opportunity to take cover or to leave,” said Retired Army Maj. Gen. Robert Scales told The New York Times on Oct. 20.

Retired Army Brig. Gen. Mark Kimmitt told The Times that there's a difference between "strategic" and "tactical" surprise. He said "strategic surprise" — knowing that the attack is coming — is "rarely accomplished. "Tactical surprise" — exactly how the attack is coming — "is kept secret."

“Mr. Trump does not seem to understand this critical distinction between strategy and tactics," he told the paper.

John Noonan, a former Air Force captain and senior adviser to GOP presidential candidate former Florida Gov. Jeb Bush, echoed that criticism on Monday.

Does @realDonaldTrump understand that Mosul is a strategic objective? That it's no secret the Iraqis would take it back? — John Noonan (@noonanjo) October 24, 2016

Some critics blasted Trump for predicting the failure of the Mosul campaign before the Iraqi forces even reached the city.

"Shameful that @realDonaldTrump has declared the battle for Mosul a failure before it's really even begun," tweeted former CIA and Pentagon senior official George Little, who is supporting Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE.

Shameful that @realDonaldTrump has declared the battle for Mosul a failure before it's really even begun. Another reason #ImWithHer. — George Little (@georgelittledc) October 24, 2016

U.S. and coalition partners are also assisting in the Mosul offensive.

Between 100 to 200 U.S. troops are embedded with the Iraqi and Kurdish peshmerga units as they advance towards Mosul, and there are hundreds more U.S. forces who are assisting with the operation at headquarters farther back.