Ukraine's offensive against Russia is missing a key element because no allies sent F-16 jets fast enough: expert

• Ukraine is launching a major counteroffensive to bring the fight to the Russians.
• But an expert said it will likely suffer from a significant capability gap: close air support.

Ukraine's long-awaited counteroffensive against the Russian invading force appear to be underway.

The country is bristling with new and powerful equipment from Western allies — from long-range missiles to advanced tanks to infantry fighting vehicles.

But one expert cautioned that Ukraine's chances of success may be blunted by a looming gap in Ukraine's military that Western help has so far done little to fill: its air force.

Michael Clarke, a visiting professor at the respected Department of War Studies at King's College London, gave the assessment as part of a broader look at the counteroffensive published by The Times of London.

He said that a key challenge Ukraine will face trying to break through Russia's thick defenses in the south of the country is taking out its artillery.

Russia's dominance in artillery has been one of the defining features of the conflict so far, and Ukraine doesn't have that many ways of countering their superiority in the number of artillery pieces and their stockpile of ammunition, which allows Russia to fire many times the shells that Ukraine can.

Per Clarke: "We'll also see if their rockets are enough to knock out the covering Russian artillery fire. Because this is where they'll feel their lack of aircraft to attack those, the close air support which F-16s would do very well."

Close air support is pretty much what it sounds like — aircraft working closely with ground units, usually to clear out obstacles or damage key positions or weapons so that foot soldiers and armor can advance.

It is a sophisticated way of fighting that involves good coordination — and which Russia has often struggled to pull off when fighting in Ukraine.

The F-16 — a US-made fighter jet fielded by numerous NATO countries — has been the most prominent item on Ukraine's military wishlist that it has so far not been able to get.

The F-16 has distinguished itself in the past in close air support, including in the Kosovo War, the First Gulf War and in the US invasion of Afghanistan.

President Volodymyr Zelenskyy and his allies lobbied for months to get hold of some of the jets to help even the odds against Russia's larger and better-equipped air force.

Even as it acquired longer-range missiles, the Patriot air-defense system, and advanced Western tanks, modern fighter jets remained out of reach.

Another big gap is air-defense systems mobile enough for the Ukrainians to bring with them as they advance to keep Russia's attack aircraft at bay.

In late May, Ukraine's lobbying finally succeeded, with the Biden Administration agreeing that F-16s should be sent to Ukraine, though possibly by other allies rather than the US itself.

But the lead time is so long that it won't be able to use them any time soon.

As a Pentagon spokesman said in a recent briefing, F-16s to Ukraine is a "long-term" endeavor and "will not be relevant to the upcoming counter offensive."

As Insider's Ryan Pickrell reported earlier this week, Ukraine is facing a tough challenge trying to advance on Russia, even with its advanced weaponry.