Russian President Vladimir Putin says the country's rule over all four Ukrainian regions it unilaterally claims to have annexed must be recognized in order for peace talks to take place.

Putin spoke with reporters at a regional summit in Kyrgyzstan on Friday.

He said the peace process "will probably be complicated and will take some time." He added, "The parties to this process will have to accept the realities that are taking shape on the ground."

Meanwhile, White House National Security Council Coordinator for Strategic Communications John Kirby says US intelligence analysis shows that Russia and Iran are considering setting up a drone assembly line in Russia.

Kirby also said Russia may be providing helicopters and air defense systems to Iran in return. He said Russia is offering Iran an unprecedented level of military and technical support.

Britain's defense ministry said on Saturday that "Iran's support to Russian forces is likely to expand in the coming months," and that "Russia is attempting to obtain more weapons, including hundreds of ballistic missiles."

The ministry says, "If Russia succeeds in bringing a large number of Iranian ballistic missiles into service, it will likely use them to continue and expand its campaign of strikes against Ukraine's critical national infrastructure."