Russian President Vladimir Putin with Defense Minister Sergei Shoigu, left, and Federal Security Service Director Alexander Bortnikov. REUTERS/Maxim Shemetov/File Photo Russian Foreign Minister Sergei Lavrov told reporters Monday that Russia would provide "the most active" support to the Syrian army to keep the strategic city of Aleppo and the surrounding area from falling into the hands of "terrorists."

"What is happening in and around Aleppo now is what we had warned the Americans about beforehand — and they know it: that we will in the most active way support the Syrian army from the air not to allow the seizure of this territory by terrorists," Lavrov said.

Lavrov's comments, which come one day after Russia's deputy defense minister announced that there was still "much to be done to support the Syrian army" — have added to speculation that Russia is preparing to revamp its military operations in Syria three months after announcing it had begun to withdraw.

Moscow intervened on behalf of embattled Syrian President Bashar Assad in September, turning the tide of the war in Assad's favor with relentless airstrikes targeting anti-Assad rebels near Turkey's border and Aleppo, which is now the war's epicenter.

Putin shocked the world when he announced in March that Russia would begin to withdraw "the main part" of its military presence in Syria four months after intervening. Jeff White, a defense fellow at The Washington Institute for Near East Policy, told Business Insider at the time that Putin had "left some important military tasks unfinished," including the encirclement of Aleppo.

Perhaps for that reason, Russia left many of its military resources in Syria intact in the event it would need to re-escalate.

"The notion that Russia needs to 'return' to Syria is fallacious," Mark Kramer, the program director for the Project on Cold War Studies at Harvard's Davis Center for Russian and Eurasian Studies, told Business Insider on Monday.

"Even after Putin announced that Russia was ending its military operation a few months ago, Russian planes continued to provide bombing support for Syrian forces, albeit much less frequently than before," he added.

Experts say it now appears Moscow is setting the stage for a large-scale offensive against Syria's more mainstream opposition, considered terrorists by forces loyal to Assad, by ramping up its antiterrorist rhetoric, reinforcing its ground role via military advisers and private contractors, and escalating the rate and breadth of airstrikes around Aleppo's frontlines and in Idlib province.

On Saturday, the former chief of the general staff for the Russian armed forces said Russia "should act more forcefully" against Syria's "terrorists," who were given time to prepare for an offensive by the cessation-of-hostilities agreement brokered between the US and Russia in late February.

The French daily newspaper Le Figaro reported in early May that Russia had contracted private "mercenaries" to fight for Assad, and Al-Monitor reported last week that ground forces and paratroopers had been deployed to Russia's port on Syria's western coast "to support more than 3,000 Russian volunteers dispatched to the region in the last few weeks, in a bid to revive coordination with the Syrian Arab Army."

The rate and breadth of Russian airstrikes in Aleppo and opposition-held territory in Idlib province tripled over the course of three days last week, according to the Institute for the Study of War, marking what it called "a dangerous shift in the Russian airstrike pattern to levels only seen prior to the brokering of the cessation of hostilities agreement in late February 2016." Residents with a Nusra Front flag in April 2015 during a demonstration celebrating their takeover of Idlib and calling for the implementation of the Islamic Sharia law, in Al-Sakhour neighborhood of Aleppo. Hosam Katan/Reuters Zeina Khodr, a correspondent for Al Jazeera based out of Doha, put it bluntly: "Moscow may be justifying and paving the way for a large-scale offensive against [Al Qaeda affiliate] Jabhat al-Nusra." In that way, however, Russia is evidently also preparing for a large-scale offensive against Syria's mainstream rebels — many of whom have continued to coexist with Nusra in the name of survival. "I have an impression, which is supported by yet unconfirmed facts, that these [moderate] groups intentionally occupy al-Nusra front positions in order to prevent al-Nusra from being attacked," Lavrov told Sputnik News last month. That Nusra is not protected by the terms of the cease-fire has created a loophole for the Russians to attack mainstream rebel groups in the midst of the cease-fire. Many of these groups are backed by the West, and that some have reportedly chosen to coordinate with Nusra against forces loyal to Assad "has exposed the Achilles' heel of the American strategy in Syria: the line between terrorist and 'moderate rebel' is pencil-thin." That is according to The Daily Beast's Nancy Youssef, who was told last week by a US intelligence official that Lavrov's recent proposal that the US and Russia coordinate their airstrikes in Syria to target Nusra militants "was a blatant attempt to deflect attention from the targeting of moderate opposition" forces in Syria.

Protesters with Free Syrian Army flags and chanting slogans during an antigovernment protest in the town of Marat Numan in Idlib Province, Syria, on March 4. REUTERS/Khalil Ashawi "Despite claims they are focusing on" Al Qaeda in Syria and ISIS, the official said, "Russia and Assad have primarily targeted the moderate opposition."

Lavrov offered to halt airstrikes long enough to allow the rebels to back away from Nusra positions, but the US refused the proposal.

The rebels did not back away despite urging from US Secretary of State John Kerry, and Moscow is evidently now taking advantage of a lack of "cooperation" from Washington and stalled peace talks in Geneva — Mohammad Alloush resigned from his position as the opposition's chief negotiator last month — to re-escalate its military presence.

"It can be said that for the first time the military and the diplomatic positions have converged on the need to restrengthen [Russia's] credibility," Mohammad Ballout wrote in Al-Monitor on Friday. "This might pave the way for a partial re-adoption of the military option."

Kramer, of Harvard, noted that Russia "may well escalate its operations back up to something close to their October through March levels."

"But if so," he added, "that would represent a fairly embarrassing admission that the Syrian regime is unable to sustain progress on its own."