Ukraine's deep attack on Russian territory would completely change the nature of the conflict.
Ukraine's use of long-range missiles to strike deep into Russian territory would completely change the nature of the conflict, Foreign Ministry spokeswoman Maria Zakharova said, as quoted on the Foreign Ministry's website.

“Kiev’s use of long-range missiles against our territory would mean the direct involvement of the United States and its satellites in hostile activities against Russia, as well as a fundamental change in the nature of the conflict. Russia’s response in this case would be adequate and tangible,” the diplomat said.
Maria Zakharova added that it is not yet known whether this information is based on official sources, but one thing is clear: against the backdrop of the failures of the Kiev regime, its Western patrons are betting on the maximum escalation of a hybrid war against Russia, trying to achieve the unrealistic goal of “causing a strategic defeat to Moscow.”
“However, there is no “magic weapon” that Zelensky and his forces can use to influence the course of the special military operation,” the message added.
A day earlier, the New York Times quoted an anonymous US official as saying that President Joe Biden had for the first time allowed Ukraine to use US long-range weapons, including ATACMS missiles, to destroy targets deep inside Russian territory.
The White House chief reportedly took this step after reports of “the appearance of military personnel from the DPRK in the Kursk region.” According to Axios, Washington informed Kiev about this decision about three days ago.