The al-Qaeda wing in Syria may have succeeded its Yemen-based counterpart as the jihadist group’s largest and strongest affiliate, the U.S. government and some experts suggested this week.

U.S. officials have already warned of “grave consequences” if the al-Qaeda branch in Syria is allowed to thrive.

Al-Qaeda has established its local branch as one of the most dominant opposition groups in Syria and has quietly amassed its “largest guerrilla army in history,” terrorism expert Thomas Joscelyn, of the Foundation for Defense of Democracies (FDD), told VICE News, echoing U.S. officials.

“In recent years, al Qaeda has extended its influence through newly empowered local proxies, and in Syria’s Idlib province the terror outlet has won valuable territory in the heart of the Middle East,” also notes VICE, adding: “Al Qaeda, through its local affiliate, the militant alliance Hayat Tahrir al Sham (HTS, also known as Organization for the Liberation of the Levant), recently cemented its dominance in the northwest province of Idlib by seizing territory from rival rebel group Ahrar al Sham.”

In 2015, al-Qaeda in the Arabian Peninsula (AQAP) in Yemen emerged as the terrorist group’s most dangerous and potent threat against the United States.

Although some officials and experts are now suggesting the group’s Syrian wing may be the largest and strongest al-Qaeda branch in the world, others believe AQAP still remains a top threat.

The ongoing civil war in Yemen, which has pitted U.S.-backed Saudi Arabia against Iran-allied Houthi rebels, has helped AQAP “become stronger than at any time since it first emerged almost 20 years ago,” reported Reuters in April 2016.

Later that year, Brett McGurk, then-President Barack Obama’s special envoy for the U.S.-led coalition against the Islamic State (ISIS/ISIL), declared that the Syrian al-Qaeda affiliate was becoming the “largest” al-Qaeda offshoot “in history.”

In July 2017, as President Donald Trump’s envoy, McGurk declared that Syria is now home to “the largest al-Qaeda safe haven since 9/11.”

Katherine Zimmerman from the American Enterprise Institute (AEI) told U.S. lawmakers last month that al-Qaeda has set the conditions to establish an Islamic emirate in Syria.

Zimmerman said, “Al Qaeda is strongest in Syria, where it has used the conditions created by the Syrian civil war and [the U.S.-led coalition’s] Operation Inherent Resolve against ISIS to establish deep sanctuary in the northwest and position itself to expand farther into the Syrian theater.”

Al-Qaeda has reportedly benefited from the U.S.-led coalition’s single-minded focus against ISIS and exploited the opposition against Syrian dictator Bashar al-Assad to grow stronger.

Various experts, including Zimmerman, believe that al-Qaeda will likely incorporate the remnants of ISIS if the terrorist group falls.