Despite the fragile “cessation of hostilities” over much of Syria, a steady barrage of Russian air strikes is still aimed at moderate and U.S.-supported rebel forces, further complicating desperately strained humanitarian relief efforts and preparing the way for a renewed offensive by the dictatorial regime of Bashar al-Assad, say experts keeping tabs on the air assault.

“The air strikes definitely seek to give regime forces a tactical advantage” says Genevieve Casagrande, an analyst at the Washington-based Institute for the Study of War, which monitors and confirms the Syrian attacks. “The question is when they intend to make use of it.”

The air assault is a strong indication that the Assad regime’s Russian allies do not intend to be deterred or even delayed in their military planning and battlefield preparations by the on-again, off-again peace talks between the regime and the non-radical opposition forces in Syria, which are now slated to start on March 9, two days later than originally planned.

United Nations special envoy for Syria Staffan de Mistura told wire services that the delay was for “logical and technical reasons and also for the ceasefire to better settle down.”

In fact, according to Casagrande, the bombings never ceased, but instead were reduced in tempo and altered in terms of targeting. They “are continuing at a steady rate,” she told Fox News. “A lot of it is just not being talked about.”

Indeed, that is currently something akin to the official position of the U.S. State Department. Queried about the assaults, a State Department official pointed to a Monday statement by Secretary of State John Kerry, who reported, after “a couple of conversations” with Russian Foreign Minister Sergei Lavrov, that “we have agreed that while there have been some number of violations reported on both sides and we take them all very seriously, we do not want to litigate these in a public fashion in the press.”

Kerry added, “We want to work to eliminate them, and we have agreed on a process by which we will do that.”

So far, however, the major difference is that the Russian strikes are now taking place behind the front lines of combat between regime forces and the non-radical opposition, and thus have less visibility than waves of Russian air attacks late in February—right up to the Feb. 27 start of the “cessation”-- that indiscriminately hit civilian targets and caused tens of thousands of additional Syrian refugees to flee toward the northern Syrian border with Turkey.

The assaults “appear to be hitting rural towns along opposition supply routes” especially to the west of Aleppo, Syria’s second largest city and an increasingly encircled stronghold of opposition to the Assad regime, Casagrande told Fox News.

They “are largely aimed at logistics and communications,” Casagrande told Fox News and could “facilitate the eventual movement of regime ground forces.”

In fact, some of those movements may already be taking place. A spokesman for The Syria Campaign, a media group with ties to non-radical Syrian opposition forces, told Fox News that on-the-ground observers were charging that the air strikes were part of a deliberate strategy to quietly gain more territory.

The spokesperson said the observers claimed Russian and regime forces were “bombing roads so that they are disconnecting some parts of the liberated areas” controlled by the opposition. Meantime, the spokesman claimed that “hundreds” of regime soldiers were massing in various areas, notably moving toward the near-destroyed western provincial city of Homs and had taken control of formerly rebel areas south-west of Damascus.

In the shorter term, the attacks are crimping the movement of supplies and humanitarian assistance into Aleppo from the west, after the earlier attacks shut down major supply routes into the city from the north.

For international non-governmental organizations that deliver cross-border humanitarian aid into Syria—United Nations relief organizations inside the country work under the say-so of the Assad regime itself —the earlier round of assaults proved especially stifling.

The U.S.-based aid organization Mercy Corps, which has no links with Assad, reports that in February it could only deliver humanitarian supplies of food and emergency shelter to about 180,000 people monthly, vs. its previous average of 500,000.

While saying that the organization “needed more time before we can say the cessation of hostilities is holding,” Christine Bragale, Mercy Corps’ director of media relations, told Fox News that the group was making “daily, sometimes hourly, assessments” of the dangers posed to the relief effort.

Despite the pressure, Mercy Corps “continues to deliver humanitarian support into northern Syria,” she said, including Aleppo, where some 66,000 people are dependent on the organization’s help.

“We have seen some of our access routes exposed,” she added, and a number of Mercy Corps aid workers in Syria—who are all Syrian citizens—are themselves living with their families in refugee camps.

Overall, humanitarian aid remains drastically insufficient: “We are delivering every last piece of supplies that we can, and it’s not enough,” she said.

Moreover, she added, “Mercy Corps absolutely believes that humanitarian access cannot be used as a bargaining chip in any negotiations. We cannot use the lives of men, women and children as part of this process. The situation in Syria is morally unacceptable.”

The situation is far worse in areas of Syria where at least 100,000 Syrians, and perhaps many more, are holding on in more than a dozen besieged areas that are in the overwhelming number of cases cut off by Assad regime forces (and, in a couple of cases, by the radical jihadists of ISIS and other organizations).

In the long-besieged suburb of Moadamiyyah, outside Damascus, a local resident who calls himself Dani Qappani told Fox News that a much heralded one-time aid delivery by a United Nations convoy—one of a handful approved by the Assad regime in advance of the “cessation of hostilities”—had made a difference, at least for a time.

“People have food for one month,” he told Fox News in a long-distance interview. “But today they were supposed to bring medicine but we didn’t get it.” His town was still besieged by a combination of Assad regime forces and fighters from Hezbollah, the radical militia supported both by the Assad government and by Iran.

The nearby southern city of Daraya is still cut off completely from outside humanitarian aid, he reported, and “there have been many violations of the ceasefire by Assad in rural areas.”

Nonetheless, he added, rebels were adamant that the bombings must stop and sieges before lifted before true peace talks could start.

And one other demand remained non-negotiable: “Assad has to go.”

George Russell is editor-at-large of Fox News and can be found on Twitter: @GeorgeRussell or on Facebook.com/GeorgeRussell