US is said to believe Ukraine can keep control of Kyiv for another 4 to 6 weeks, according to NBC News

• A US official told NBC News that the US thought Ukraine could keep control of Kyiv for weeks longer.
• The official said Russian troops were in a strong position to encircle the city.

Two weeks in to Russia's invasion, a US official on Thursday told NBC News that US intelligence believed the Ukrainian capital, Kyiv, could hold out for at least another month.

The official said that Russia's troops were considered capable of encircling Kyiv in as little as a week but that the latest estimates by US intelligence — subject to change — were that Ukrainians could maintain control of Kyiv for another four to six weeks.

Neither the Department of Defense nor the White House immediately responded to requests for comment from Insider.

Prior to the invasion, Russian President Vladimir Putin is widely thought to have believed his forces would be able to capture Ukraine's capital in a matter of days. But a series of early-stage Russian failures amid the country's chaotic initial assault left Ukraine in a stronger-than-expected position.

The US official told NBC that Ukraine is using a layered, mobile defense, which utilizes fast "hit-and-run" attacks with light infantry and anti-armor weapons. Ukrainian troops also have the advantage of fighting in their own country with intelligence assistance coming in from local citizens on the ground, the official said.

The Russians, however, are still in a powerful position and there is a limit to how long Kyiv can hold out. Lt. Gen. Scott Berrier, the director of the Defense Intelligence Agency, told The New York Times earlier this week that Ukraine's hold on Kyiv could be running out of time.

"With supplies being cut off, it will become somewhat desperate in, I would say, 10 days to two weeks," he told the outlet.

The newspaper reported that other estimates are similar. Some allied governments think Russia will completely surround Kyiv in a week, estimating Ukraine will then manage to hold on to the city for another month, according to the outlet.

And as Putin's determination intensifies along with Ukrainian defiance, some experts fear the war is likely to escalate. William Burns, CIA director, told The Times that he is expecting an "ugly next few weeks."