(WASHINGTON) -- The Pentagon has been providing daily updates on the Russian invasion of Ukraine and Ukraine's efforts to resist.
Here are highlights of what a senior U.S. defense official told reporters Monday on Day 26:
Russia uses hypersonic missile against Ukraine: Biden
President Joe Biden confirmed Monday night that Russia has used a hypersonic missile in Ukraine, saying it’s “the only thing that they can get through with absolute certainty.”
"It doesn't make that much difference, except it's almost impossible to stop it. There's a reason they’re using it," Biden said at the Business Roundtable’s CEO Quarterly Meeting in Washington, D.C.
Earlier on Monday, a senior U.S. defense official could not confirm Russia's claims to have used hypersonic missiles in Ukraine, but said it's not clear why it would.
"It's a bit of a head-scratcher to be honest with you, because it's not exactly clear why, if it's true, would you need a hypersonic missile fired from not that far away to hit a building?" the official said.
One of the major advantages of hypersonic weapons is the ability to evade radar detection from distant targets. But for hitting nearby Ukraine, the advantages are less obvious.
One reason Russia might have used such a weapon could be due to running low on precision-guided munitions, or to send a message to the West and Ukraine in order to gain leverage in negotiations, the defense official said, adding that it is not practical from a purely military perspective.
No Russian progress on the ground
Russian forces are no closer to Kyiv than they were more than a week ago, the official said.
"They haven't achieved anything in terms of what we assessed to be their objectives, which was population centers so that they could occupy and take over Ukraine," the official said.
The official added that you can count "on one hand" the cities Russian forces have taken, noting that Donetsk and Luhansk were already under their control before the invasion.
"So what have they gained in now 26 days? They got Melitopol, they got Berdyansk, and they got Kherson. That's it. They don't have Kharkiv, they don't have Mariupol," the official said.
Ukrainian forces even mounted a counter-attack to try to retake Kherson, according to the official.
"It's very clear that the Ukrainians are showing no signs of stopping the resistance and no signs of slowing down their attacks on the Russians," the official said.
The official said most credit for the stalled Russian efforts goes to the Ukrainian forces and citizens, and the leadership of President Volodymyr Zelenskyy.
"President Zelenskyy has been quite inspirational, as you've all seen, and has really motivated his forces and his citizens, because some average citizens are picking up arms and fighting," the official said.
But weapons and training from the U.S. and others are also playing a major role.
"It's not just about pointing and shooting," the official said. "They're able to be nimble and creative because they were so well trained over the last eight years."
Despite setbacks, Russian forces have most of their forces intact and are trying to overcome.
"They are looking for a chance to gain some momentum -- not even regain momentum ... because they never really had it. And that's what's so frustrating for them," the official said.
The frustrated Russian ground effort is leading to more missile strikes and artillery bombardment on cities, which makes things ever more dangerous for civilians, according to the official.
"This is not a military known for precision," the official said of the invaders.
Pentagon press secretary John Kirby told reporters Monday the Pentagon believes Russia is in some cases deliberately targeting civilians.
“We certainly see clear evidence that Russian forces are committing war crimes," Kirby said. "And we are helping with the collecting of evidence of that. But there's investigative processes that are going to go on and we're gonna let that happen. We're going to contribute to that investigative process.”
Failure to launch
The U.S. assesses Russia has fired more than 1,100 missiles against Ukraine since the beginning of the invasion. And there are indications it is having "inventory issues" with its precision-guided munitions, which could be one reason we're seeing greater use of unguided "dumb bombs," the official said.
The official added that Russia still has the majority of its missile stocks available.
But the Pentagon is also seeing problems with the reliability of Russia's precision weapons. Some Russian missiles are "failing to launch, or they're failing to hit the target, or they're failing to explode on contact," the official said.
More Russian naval action near Odessa
While there is still no sign of an imminent amphibious assault, the U.S. has seen more naval activity in the northern Black Sea, where Russia has more than a dozen surface warships of varying types.
"Clearly they're using surface combatants for shelling purposes, and for the long-range fires in and around Odessa," the official said. "Whether this is a prelude to an amphibious assault is not clear."
Russian combat power
Russia's invading force has "just below" 90% of its combat power intact, according to the official.
"We recognize that they are taking casualties every day. They are losing aircraft, they are losing armor and vehicles -- there's no doubt about that. Tanks, APCs, artillery units, helicopters, fixed wing jets," the official said.
As for Ukraine, the Pentagon assesses it still has more than 90% of its combat power intact. The official credits this to the constant arms replenishment coming in from the U.S. and others. Also keep in mind that while this estimated percentage is slightly higher for Ukraine than Russia, Russia has more total power to lose.
So far, the U.S. hasn't seen any movement of additional Russian troops to Ukraine.
Russia lacks small-unit leadership
The official could not confirm Ukrainian claims to have killed six Russian generals, but said it makes sense that there would be senior officers on the ground with the invading force.
First, this is a major operation for the Russian military
Second, "they don't organize their military the way we do, they don't have an equivalent to a noncommissioned officer corps. And their junior officers don't have the same wherewithal, flexibility -- they don't invest in their junior officers the kind of initiative that we do," the official said.
While the U.S. military instills a sense of battlefield leadership starting at the junior NCO ranks (corporals and sergeants on up), the Russian military has no such ethos, according to the official.
"The fact that there might be senior leaders on the field perhaps involved at a more tactical level than we would have a two star or a one star, it's apples to oranges in terms of how they organize themselves and how they lead," the official said, adding that Russian forces seem to be having command-and-control problems.
$800 million weapons package from US shipping soon Initial shipments of the new $800 million U.S. weapons package to Ukraine will arrive "very, very soon," the official said. This package includes thousands of shoulder-fired anti-armor/air systems, small arms, and 100 small Switchblade drone systems.
The Pentagon has not seen any attempts by Russia to hit incoming weapon shipments so far.
ABC News' Justin Gomez and Luis Martinez contributed to this report.
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