Update(1230ET): Putin says not so fast... First, here's a UK Times report within the last hour:

Britain and the United States are on the verge of allowing Ukraine to use long-range missiles against targets in Russia after accusing President Putin of “escalating” the conflict by accepting ballistic missiles from Iran.

David Lammy, the foreign secretary, and Anthony Blinken, the US secretary of state, said they would return to their respective countries to inform their leaders of the “operational details” surrounding Ukraine’s use of weapons such as Storm Shadow missiles after meeting President Zelensky in Kyiv.

Blinken promised to work quickly on Ukraine’s requests to ease the restrictions, saying he would take what he had learnt “back to President Biden.” —Putin escalating conflict, say western allies as missile approval moves closer

President Putin is currently speaking at the St. Petersburg International United Cultures Forum, which addresses current events related to Russia. He issued the following red line while speaking to a reporter on the sidelines of the conference Thursday:

Putin says long-range arms for Kyiv would mean 'NATO countries at war with Russia'