Ukrainian President Volodymyr Zelensky last week urged US President Donald Trump to supply the long-range missiles, according to a report by the Axios news outlet, saying Kyiv could use them to strike targets deep inside Russia, including near Moscow.
US Vice President JD Vance said on Sunday that Washington was considering Ukraine’s request.
Speaking at the Valdai Discussion Club in the Black Sea resort of Sochi on Thursday, Putin said Tomahawks posed a serious threat and would require American involvement, the Reuters news agency reported.
"It is impossible to use Tomahawks without the direct participation of American military personnel," Putin said.
"This will mean a completely new, qualitatively new stage of escalation, including in relations between Russia and the United States," he added.
Putin said Russia would strengthen its air defences and shoot down the missiles if they were supplied, Reuters reported.
It cited two US officials on Wednesday as saying Washington would share intelligence on long-range energy infrastructure targets in Russia while weighing whether to provide Ukraine with missiles capable of hitting them.
Source: Reuters, PAP