(CNN) The Biden administration is unlikely to significantly change its approach to helping Ukraine fight Russia, sources tell CNN, and is rebuffing some Ukrainian weapons requests for now -- even as Ukrainian forces have made sweeping gains and recaptured thousands of miles of territory from Russia in recent days.
US officials broadly view Ukraine's recent momentum as evidence that the types of weapons and intelligence that the West has been providing to Ukraine in recent months has been effective. And some caution that it's too early to call Ukraine's rapid progress in recent days a turning point in the war, warning that Russia is far from a spent force militarily.
Officials do not believe the battlefield landscape has changed enough to warrant a dramatic strategy shift in the short term despite recent Ukrainian requests to lawmakers and the Pentagon for long-range missile systems and tanks, which they assert can help them sustain the push for longer and keep the territory they have regained.
But for now, at least, the US is still not inclined to provide Ukrainian forces with the long-range Army Tactical Missile Systems, also known as ATACMS, that they have been requesting for months, officials told CNN. ATACMS have a range of up to 300 kilometers, or around 185 miles. The administration still believes providing those systems could be escalatory because they could be used to fire into Russia itself. Currently, the maximum range of US-provided weapons to Ukraine is around 49 miles.
"It's our assessment that they don't currently require ATACMS to service targets that are directly relevant to the current fight," Under Secretary of Defense for Policy Colin Kahl told reporters in late-August.
Last week, Defense Secretary Lloyd Austin intimated the US position hasn't shifted. "The HIMARS, using the GMLRS rockets, have been extraordinary in terms of enabling the Ukrainians to service the targets that they need to service inside of Ukraine," Austin said in Prague on Friday, making no mention of ATACMS.
Since the beginning of the conflict in February, the Biden administration has taken an incremental approach to providing arms to Ukraine -- in some cases, later agreeing to send weapons that earlier in the conflict would have been deemed far too escalatory. Its calculus has largely been based on avoiding systems that might be seen by Putin as too provocative, although those lines have moved over time and been criticized by some former officials as arbitrary.
Some US military officials also acknowledged that systems currently considered too escalatory -- like F-16 jets, for example -- might eventually be provided to Ukraine. But those sources cautioned that such a decision is likely far in the future and isn't linked to Ukraine's recent, but nascent, successes. And there are no indications that such discussions are underway now.
"Ukraine has made some progress, but there's still a very tough fight, and a tough fight ahead, so I think we also need to keep that in mind," Pentagon press secretary Brig. Gen. Pat Ryder told reporters on Tuesday. "I think it is reasonable over time to continue, as we have, that dialogue to hear what their needs are, to work with the international community."
US National Security Council coordinator for strategic communications John Kirby echoed that, telling reporters that the US would likely announce additional military assistance to Ukraine in the coming days but declined to outline that aid in detail.
Another defense official told CNN on Tuesday that the longer-range equipment is likely still off the table for now because Ukraine is "still in the sweet spot on HIMARS," or High Mobility Artillery Rocket Systems that the US and some of its allies provided to Ukraine over the summer. The munitions for those systems, provided by the US, are capable of using GPS-guidance to strike a target with precision some 40 miles away.
Ukrainian forces have received "thousands" of GMLRS rounds, Joint Chiefs of Staff Chairman Gen. Mark Milley said last week, and used them to strike Russian ammo depots, logistical hubs and command posts.
Still, some lawmakers disagree with the administration's cautious approach.
Asked whether he believes the US should send the ATACMS, Republican Sen. Marco Rubio of Florida told CNN, "I think we should send them anything they need to reclaim their territory, to the extent that we have it available, and it is reasonable."
"I think the concern some would say is that the longer-range missiles could target deep inside of Russia and trigger a broader conflict. I'm not sure I'm as troubled by that," Rubio added.
The US has also been careful not to call the rapid Ukrainian territorial gains a turning point in the war, or a critical moment that will decide the outcome for good.
"It's more important than ever that we don't appear to be spiking the ball," a defense official said. The Russians still have a tremendous amount of firepower, manpower and equipment in the fight in Ukraine, and the victories this month of the Ukrainian military have not sealed the outcome of the war. In military terms, Russia still has "mass," even if it has been unable to bring that to bear at a critical time and place to shape the outcome of a particular fight.
Still, the Ukrainian counteroffensive -- planned with US assistance -- does appear to have been "expertly executed," the official said.
One thing that has changed in the last several months is the Ukrainians' willingness to share intelligence with the US, allowing American officials to better help the Ukrainians shape their battlefield operations.
"There's a lot more trust now than there was at the beginning of the war," said one Ukrainian source close to President Volodymyr Zelensky. "And the Ukrainians recognize that the more they share, the more they are likely to get in return."
A US military source added that there has been "decent communication at varying levels about what's being planned on the political side and the military side. There's pretty good military transparency."
In Kherson, where Ukraine telegraphed its intentions for months before the counteroffensive began, Russia had time to prepare, digging in to protect the territory around one of the first cities they occupied early in the war. Ukraine's advances there have been incremental and deliberate, one official said, and there is no rapid advance through collapsing Russian lines.
Some analysts have described the Kherson offensive as a "fixing" operation designed to keep Russian troops engaged away from the fight in Kharkiv.
In Kharkiv, however, the attack caught the Russians by surprise and without any well-prepared defenses, allowing the Ukrainian military to rapidly reclaim thousands of square miles of territory.
Russia has so far failed to meaningfully stop the counteroffensive in Ukraine's south or east as the problems they had early in the war -- supply line issues, logistical problems, and a lack of effective command and control -- still plague the Russian military, officials said. Russia proved unable to hold the territory it had seized, partially because of the high cost imposed on them by Ukrainian defenders.
The US is less concerned about Ukraine's ability to hold reclaimed territory, officials said, even in the east, where Ukrainian forces have moved more than 60 kilometers within days in some cases. Ukraine's supply lines are internal, whereas Russia's were outside its own borders.
In addition, Ukraine's forces will get a significant boost to morale and will from the recent victories, one official said, while Russia's depleted forces will feel the opposite.
It's "not a real concern of [Ukraine] overstretching supply lines," an official said. Despite Russian claims of destroying the US-provided HIMARS, all of the 16 systems remain accounted for and the "overwhelming majority" of M777 howitzers also remain in operation, officials said.