The shoot-down marks the first time a USA jet has downed a Syrian regime warplane, despite leading a massive air campaign targeting IS in Syria for almost three years.
It was the first time the United States has shot down a Syrian plane, and the first time a US military jet has shot down any manned aircraft since 1999.
"We are warning Washington not to take such actions in the future", Deputy Foreign Minister Sergei Ryabkov told the Interfax news agency.
After the three encounters, Assad's forces wheeled around and seized territory to the north all the way to the Iraqi border, leaving US forces and their allies largely isolated in the southeast and cutting off their path to the Islamic State group.
"There isn't an over-arching U.S. strategy driving this", said Charles Lister of the Middle East Institute. The review resulted in an "annihilation campaign" aimed at killing all IS fighters, and saw commanders gain greater autonomy to make battlefield decisions and approve strikes.
A US warplane shot down an armed drone linked to Syrian regime forces, the Pentagon said Tuesday, the latest in a series of incidents between USA -backed forces and the regime of Bashar Assad that threatens to escalate the conflict there.
"The Iranian position will advance", Ford said.
Like Obama, Trump has focused on Islamic State, leaving for later the question of Assad's fate and the region's mangled alliances. He spoke on condition of anonymity in line with regulations. "We remain available on our end. Our most capable allies are the (Kurdish) peshmerga, but Turkey, who is a North Atlantic Treaty Organisation ally and host to an airbase that is central to our efforts, considers the Kurds enemies". Now, the guards say the targets included an ISIS command center, a facility for making vehicle bombs.
They said hundreds of troops with dozens of armoured vehicles including tanks had surged into the Bir Qassab area some 75 km (45 miles) southeast of Damascus towards the Badia region that skirts the borders with Jordan and Iraq.
A White House spokesman did not respond to calls and an email seeking comment.
The past 48 hours have been busy in Eastern Syria.
Iran has targeted jihadists in Syria with missiles in retaliation for deadly attacks in Tehran, but the strike was also a message to its regional rivals and Washington, experts say.
The U.S. -led coalition fighting the Islamic State group said a U.S. F-15 fighter jet shot down the drone "after it displayed hostile intent" while approaching a military camp near the Syria-Jordan border.
The downing of the warplane - the first time in the six-year conflict that the USA has shot down a Syrian jet - came amid another first: Iran fired several ballistic missiles Sunday night at IS positions in eastern Syria in what it said was a message to archrival Saudi Arabia and the United States.
The Guard described the missile strike as revenge for attacks on Tehran earlier this month that killed at least 18 people and wounded more than 50, the first such IS assault in the country.
"A number of mid-range ground-to-ground missiles [were] fired from the IRGC Aerospace Force bases in Kermanshah and Kurdistan provinces", according to a statement from the IRGC announcing the attack.
The Russian defense ministry also said it is suspending an agreement to minimize the risk of in-flight incidents between Russian and USA -led coalition aircraft operating over Syria.
The Saudi navy has captured three members of Iran's Revolutionary Guard Corps (IRGC) from a boat seized last week as it approached the kingdom's offshore Marjan oilfield, the Saudi information ministry said on Monday.
Sunday's incident marks the latest in a series of United States attacks on pro-regime forces.
"As a precautionary measure, Australian Defence Force (ADF) strike operations into Syria have temporarily ceased", Australia's Department of Defence said in a statement.