The US is considering deploying Patriot surface-to-air missiles in Estonia, US Vice President Mike Pence told Estonian Prime Minister Juri Ratas on Sunday.

"We spoke about it today, but we didn't talk about a date or time," Ratas told state broadcaster ERR after the meeting.

The mobile, ground-based Patriot system is designed to intercept incoming missiles and warplanes.

"We talked about the upcoming (Russian military) maneuvers near the Estonian border... and how Estonia, the United States and NATO should monitor them and exchange information," Ratas said.

Read more: US VP Mike Pence embarks on European reassurance mission

Pence was in Estonia as part of a four-day tour to Estonia, Georgia and Montenegro. He was due to meet with the leaders of the Baltics - Estonia, Latvia and Lithuania - on Monday. Later Monday, Pence is due in Georgia, a non-NATO member which has shared concerns about Russia, and then to Montenegro, which became NATO's 29th member on June 5.

'We are with you'

Pence told Fox News that he was sent to Europe by President Donald Trump "with a very simple message."

"That is that 'America First' doesn't mean 'America Alone,'" Pence told Fox News. "Our message to the Baltic states - my message when we visit Georgia and Montenegro- will be the same: to our allies here in Eastern Europe, we are with you."

Ratas said in a statement that the US was vital to the security of the region.

"NATO's collective position of deterrence and defense has strengthened in the Baltic region and the USA is indispensable to ensuring the security of our immediate neighborhood, as well as all of Europe," Ratas said.

Lithuania keen for missiles

Lithuania said it was eager to have Patriot missiles when the US military displayed the system in the country earlier this month after using them in an exercise there. Anti-aircraft defense is seen as one of NATO's weaknesses in the Baltic states.

Read more: Lithuanians delight in tank parades as NATO forces arrive for military exercises

In the Estonian capital of Tallinn, Pence spoke strongly but generally about the US support for eastern European countries.

He said the Trump administration had "made it clear" that it was committed to NATO's Article 5, which says an attack on one member was an attack on all. Trump had previously been criticized for failing to pledge commitment to the agreement.

The former USSR Baltic states have been gripped by fears of Moscow after Russia annexed Crimea from Ukraine in 2014 and increased military exercises.

Read more: What are Russia's Zapad war games?

aw/jm (AFP, AP)