WASHINGTON - Ukrainian forces have begun “shaping” operations in southern Ukraine to prepare the battlefield for a significant Ukrainian counteroffensive, two senior US officials briefed on the intelligence told CNN on Monday.

Shaping operations are standard military practice prior to an offensive and involve striking weapons systems, command and control, ammunition depots and other targets to prepare the battlefield for planned advances.

The US believes the Ukrainian counteroffensive, which has long been anticipated, will include a combination of air and ground operations. Ukraine indicated Monday morning that the actions were underway.

“Yes, (Ukrainian forces) have started the offensive actions in several directions on the South front towards liberating the occupied territories,” Natalia Humeniuk, a spokesperson for Ukraine’s Operational Command South, told CNN, adding, “All the details will be available after the operation is fulfilled.”

US believes, Ukrainian counteroffensive, which has long been anticipated will include a combination of air and ground operations

The plans come as Russia’s war in Ukraine has passed its six-month mark, with US assessments indicating that Russia has been able to deploy fewer units to the frontlines than initially thought, according to a senior US official.

The official said many of the existing units -- which Russia organizes into Battlefield Tactical Groups, or BTGs, comprising infantry, tanks, artillery and air defense -- are deploying below strength, some even at half their normal manpower. The US has also been observing Ukrainian forces benefiting from the use of US- and NATO-supplied HIMARS mobile rocket launchers, which have allowed Ukraine to strike and destroy targets in Russian-held territory.

CNN reported last week that US and European officials say Ukraine has successfully used a method of resistance warfare developed by US special operations forces to fight back against Russia and bog down its vastly superior military. The Resistance Operating Concept was developed in 2013 following Russia’s war with Georgia a few years earlier but its value was only realized after Russia’s invasion of Ukraine’s Crimean peninsula in 2014.