The US is considering a request by Ukraine for long-range Tomahawk missiles, US Vice-President JD Vance has said.
However, Vance added President Donald Trump would be making the final determination on the matter.
Kyiv has long been calling for its Western partners to provide it with weapons that could hit major Russian cities far from the front line, arguing that they would help Ukraine seriously weaken Russia's military industry and bring the war to an end.
If the cost of continuing the war for Moscow is too high, it will be forced to start peace talks, deputy defence minister Ivan Havryliuk told the BBC.
Kremlin spokesman Dmitry Peskov played down Vance's suggestion, saying there was no panacea that can change the situation on the front for the Kyiv regime.
Tomahawk missiles have a range of 2,500 km (1,550 miles), which would put Moscow within reach for Ukraine.
While Vance remained ambivalent about Ukraine's request for Tomahawks in his remarks on Sunday, the US special envoy to Ukraine, Keith Kellogg, seemed to suggest Trump had already authorised strikes deep into Russian territory.
On Sunday, a massive 12-hour strike involving hundreds of drones and nearly 50 missiles left four people dead in Kyiv and at least 70 injured.
To protect its skies from ballistic missiles, Kyiv has asked its Western partners for at least 10 units of Patriot surface-to-air defence systems which can detect and intercept oncoming missiles. Earlier this month Moscow fired a record number of more than 800 drones and missiles.
As aerial attacks by Russia grow in frequency and intensity, the urgency for Ukraine to bolster its air defenses has increased.
Ukraine hopes that by acquiring long-range weapons and effective air defense systems, it can compel Russia to the negotiating table and diminish the threat against its cities.
