National security adviser John Bolton reportedly warned his Russian counterpart on Thursday that the U.S. is prepared to retaliate against Syria with stronger military force than it has used in the past should Syrian President Bashar Assad use chemical weapons.

The U.S. believes Assad has compiled and may use chemical weapons in his quest to recapture one of the country’s remaining rebel-held areas, Bloomberg reported Friday.

Since his inauguration, President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE has initiated two limited strikes on Syria under similar circumstances. But sources told Bloomberg that Bolton's warning to Russia was more specific than previous warnings.

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The warning comes ahead of what could become one of the deadliest flashpoints in the country's civil war, Bloomberg notes.

Syrian military forces, backed by Russian allies, are positioning themselves around the northwestern province of Idlib, the last area still dominated by rebel forces, according to Bloomberg.

The strike could magnify U.S. involvement in Syria's seven-year-old civil war — something Trump has said he wants to avoid.

On Aug. 17, the Trump administration informed Congress that it would end $200 million worth of stabilization efforts in Syria as it attempts to remove U.S. forces from the conflict.

Trump had frozen the funds in March pending a future decision, though a State Department spokesperson said at the time that the agency was committed to supporting vulnerable regions in the country.

During a speech in Ohio that month, Trump indicated that U.S. forces would be "coming out of Syria, like, very soon."

The White House declined to comment on the report.