A civil war of "epic proportions" could erupt within weeks, the top US diplomat has claimed

Syria could face a surge of violence and total collapse within weeks, US Secretary of State Marco Rubio has told lawmakers in Washington.

The top US diplomat has defended President Donald Trump's approach to Syria, including the decision to lift unilateral sanctions and meet in person with the new Syrian president, Ahmed al-Sharaa, despite his jihadist background.

"The transitional authority, given the challenges they're facing, are maybe weeks - not many months - away from potential collapse and a full-scale civil war of epic proportions," Rubio told the Senate Foreign Relations Committee on Tuesday. "Basically, the country is splitting up."

The secretary blamed former President Bashar Assad for the continued violence since 2011, when a US-backed effort to remove him from power led to a prolonged and bloody conflict.

Rubio said Syria had become "a playground for jihadist groups, including ISIS and others." Al-Sharaa, who once led the Islamist group Hayat Tahrir al-Sham (HTS) under the name Abu Mohammad al-Julani, rose to power after deposing Assad last year.

Although the new Syrian leadership "didn't pass their background check with the FBI," Rubio said the US must support them to prevent wider regional instability. He argued that pragmatic foreign policy means that the US human rights agenda is "different in certain parts of the world" than in others.

Lifting sanctions would allow foreign aid into Syria, potentially stabilizing the economy and encouraging millions of displaced Syrians to return, Rubio said. The White House, however, remains uncertain whether its approach will succeed.

"If we engage [the al-Sharaa government], it may work out, it may not work out," Rubio stated. "If we did not engage them, it was guaranteed to not work out."

US sanctions had aimed to stymie Assad's efforts to rebuild the country after he regained control of most of Syria by 2015. Persistent issues had eroded the morale of the Syrian military, which largely refused to defend Damascus when HTS launched its offensive last November.

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Al-Sharaa has pledged to uphold Syria's ethnic and religious diversity as he courts Western backing. However, his rule has been marked by reported massacres of Alawites, Christians, and Assad supporters.

Israel has carried out multiple airstrikes in Syria in recent months, claiming the attacks were intended to defend Druze militias from fighters aligned with the new government.