The United States on Tuesday offered rewards for information on three senior members of the outlawed Kurdistan Workers' Party (PKK), which has waged an armed insurgency against the Turkish state for decades.

The move could help Washington repair strained ties with NATO ally Ankara.

However, Turkey said it would approach Washington's move with caution and that Turkey expected the United States to fully cut off its ties with the Syrian Kurdish YPG militia.

Turkey has been infuriated by U.S. support for the YPG in the fight against Islamic State in Syria. Ankara considers the YPG an extension of the PKK.

On Tuesday, Washington authorized rewards of up to $5 million for information "leading to the identification or location" of Murat Karayilan, up to $4 million for Cemil Bayik and up to $3 million for Duran Kalkan.

The announcement was made by the U.S. Embassy in Ankara after a visit by U.S. Deputy Assistant Secretary of State Matthew Palmer.

The three PKK figures also appear on Turkey's "most wanted terrorists" list, according to the Interior Ministry, which describes them as being among the leaders of the organization.

Presidential spokesman Ibrahim Kalin told broadcaster Haberturk: "They [United States] say they hold the YPG separate from the PKK, but they can't fool anyone with this.

"It is a very delayed move. If they follow through, we will see it positively, but if, in the big picture, this is to veil engagement with the YPG, it will come out in a few days."

The PKK, designated a terrorist organization by Turkey, the United States and the European Union, has fought the Turkish state since 1984.

Relations between Turkey and the United States have begun to thaw since the release from jail last month of American evangelical pastor Andrew Brunson.

Last week, the two countries mutually lifted sanctions on government officials, imposed in August over the Brunson case.

Washington announced this week that Turkey would receive a temporary waiver from re-imposed sanctions on Iran.

President Recep Tayyip Erdogan said on Tuesday that talks with the United States regarding state-owned lender Halkbank, which had been facing a U.S. fine over allegations of evasion of sanctions on Iran, were on a positive track.

U.S. and Turkish troops last week began conducting joint patrols in Syria's Manbij, which the two sides have agreed to clear of militants. Turkey had previously said the United States was delaying implementation of the plan.

U.S. President Donald Trump and Erdogan are to meet this weekend at a summit in Paris.