Ukraine says it is ready to defend itself amid a build-up of Russian soldiers on its border and as tension continues to escalate between the neighbours.
Kiev's Deputy Foreign Minister Vasyl Bodnar welcomed the reported deployment of two US navy ships to the Black Sea and said it would be a politically useful tool to show that Ukraine was not alone in its dispute.
Ukraine has accused Russia of moving tens of thousands of troops to the annexed Crimean peninsula and to its eastern frontier, where a delicate ceasefire has regularly been broken in recent weeks.
Concern is growing that the long-simmering conflict in eastern Ukraine could erupt into widespread fighting following a sharp increase in violence along the front line.
Mr Bodnar said the deployment of the US navy in the Black Sea would help to strengthen Ukrainian resilience in its dispute with Russia, but questioned how American forces could practically be used if there were to be a Russian advance.
“We are ready to defend ourselves. Our armed forces and the navy are ready” to go to battle if necessary, he told a webinar organised by the Henry Jackson Society.
On Monday, the G7 urged Russia to back down and immediately de-escalate tensions.
"These large-scale troop movements, without prior notification, represent threatening and destabilising activities," the G7 foreign ministers said.
Kiev's top diplomat Dmytro Kuleba will meet Nato chief Jens Stoltenberg on Tuesday as US Secretary of State Antony Blinken also heads to Brussels for talks.
US defence chief Lloyd Austin is also in Europe and will meet his German opposite number on Tuesday morning.
The White House said last week the number of Russian troops at the border with Ukraine was now greater than at any time since 2014, when conflict erupted after Moscow seized Crimea from Kiev.
Mr Blinken warned in an interview on Sunday of "consequences" if Russia acted "aggressively" towards Ukraine.
Ukraine has urged Nato to step up Kiev's push for membership as it seeks to deter any aggression by Russia, but the alliance remains wary about speeding up plans to allow in the former Soviet nation.