Top U.S. commander warns ISIS biding its time in Syria until troops pull out

U.S. President Donald Trump is expected to declare near-total triumph over ISIS in Syria in his State of the Union address Tuesday, but American defence officials are increasingly fearful that the militants are simply biding their time until the Americans leave the battlefield as planned.

ISIS militants have lost territory since Trump's surprise announcement in December that he was pulling U.S. forces out of Syria, but a Defence Department watchdog report released Monday warns the fighters could regroup within six months to a year after the Americans leave.

ISIS "remains a potent force of battle-hardened and well-disciplined fighters that could likely resurge in Syria absent continued counterterrorism pressure," the report from the inspector general said.

The top commander of U.S. forces in the Middle East, Gen. Joseph Votel, also told the Senate Armed Services Committee on Tuesday that of the 88,000 square kilometres of territory ISIS once held, it now controls less than 52 square kilometres.

"It is important to understand that even though this territory has been reclaimed, the fight against ISIS and violent extremists is not over and our mission has not changed," said Votel, the commander of U.S. Central Command.

"The coalition's hard-won battlefield gains can only be secured by maintaining a vigilant offensive against the now largely dispersed and disaggregated ISIS that retains leaders, fighters, facilitators, resources and the profane ideology that fuels their efforts."

Votel said there are now between 1,000 and 1,500 ISIS fighters in the small area they still control in the southern part of the Euphrates River Valley near the Iraqi border. The remainder, he said, have "dispersed" and "gone to ground," suggesting they retain the potential to return.

Trump's decision to leave Syria, which he initially said would be rapid but later slowed down, shocked U.S. allies led to the resignations of Defence Secretary Jim Mattis and the top envoy to the anti-ISIS coalition, Brett McGurk.

Votel was asked at Tuesday's hearing whether he was asked for his advice about a Syria withdrawal before Trump announced his decision.

"I was not consulted," the general said.

Military pushes back on pullout

The withdrawal will fulfil Trump's goal of bringing troops home from Syria, but military leaders have pushed back for months, arguing that ISIS remains a threat and could regroup. U.S. policy has been to keep troops in place until the extremists are eradicated.

Fears that ISIS fighters are making strategic manoeuvres ahead of a U.S. pullout could also fuel criticism that Trump is telegraphing his military plans — the same thing he accused President Barack Obama of doing in Afghanistan.

Trump said in a weekend interview that the caliphate is "almost knocked out."

"We're at 99 per cent right now, we'll be at 100," he said on CBS's Face the Nation.

U.S. officials said that ISIS fighters hold only several villages in the Middle Euphrates River Valley, but added they don't expect that area to be cleared of militants for another several weeks, at best.

Officials said that overall, about 2,000 ISIS militants remain in Syria.

Rapid resurgence after withdrawal?

The Defence Department watchdog report warned that even with the ISIS forces on the run, the militant group "is still able to co-ordinate offensives and counter-offensives, as well as operate as a decentralized insurgency."

The report, which covers October through December 2018, also includes a classified section that was provided to Congress and includes a more detailed Pentagon assessment on the impact of the troops withdrawal and the status of ISIS militants and other foreign fighters in Syria.

According to the report, U.S. Central Command believes that ISIS fighters will continue to conduct "opportunistic attacks" on U.S. troops as they withdraw.

Central Command also said ISIS is "regenerating key functions and capabilities more quickly in Iraq than in Syria," but unless there is sustained counterterrorism pressure, the group's militants "could likely resurge in Syria within six to 12 months and regain limited territory" in the Middle Euphrates River Valley.

Despite Trump's order to withdraw, American officials maintain that the goal remains the "enduring defeat" of ISIS and are moving ahead with a long-planned meeting of top diplomats from the 79-member U.S.-led coalition this week. The aim of the conference is to recommit the coalition to that aim and ensure that the departure of U.S. troops does not overly complicate that mission.

Trump is expected to speak to the gathered foreign ministers at the U.S. State Department-hosted conference on Wednesday is widely expected to reiterate and expand on his anti-ISIS message from the State of the Union, officials said.