A senior pro-Russian official in the occupied Ukrainian region of Kherson told Reuters on Saturday that nearby fighting could affect the timing of its formal bid to join Russia and a decision was likely "towards next year".

Kirill Stremousov, deputy head of the Russian-backed Kherson Military-Civilian Administration, also said in a video call that the process might involve a referendum, backtracking on previous comments that none would be needed.

Asked about the timetable for joining Russia, he replied: "It won't happen by autumn. We're preparing an administrative system and then towards next year we will see what the situation is like."

Stremousov told Russian state media on May 11 that Kherson, just north of Crimea and the only regional capital that Russia has captured in more than three months of fighting in Ukraine, would ask President Vladimir Putin to incorporate it into Russia by the end of 2022. He said at the time: "There will be no referendums."

In his interview with Reuters, however, he said there could be a vote.

"We'll announce later when some kind of vote or plebiscite is planned, but it won't be today and it won't be tomorrow because our first task is to restore order in the Kherson region," he said.

Ukrainian and Western intelligence agencies have since March predicted that Moscow would hold a referendum on incorporating Kherson into Russia, as it did after seizing Crimea in 2014.

Russia has said that the fate of the Kherson region is for local residents to decide. Ukraine has pledged to expel Russian forces from all the land they have seized.

A small-time local politician and anti-vaccine video blogger before the arrival of Russian troops, Stremousov, 45, has teamed up with pro-Russian former Kherson mayor Volodymyr Saldo, serving as his deputy in the region's Russian-appointed government.

Both Stremousov and Saldo are wanted for treason by Ukraine.

Though Russian troops based in Crimea overran Kherson in the war's first days, they have failed to advance further, due to a staunch defence of the nearby city of Mykolaiv, 36 miles (58 km) away. The frontline in the area has been largely static since March.

Speaking over a video call from his office in the Kherson administration building, a portrait of Putin behind him and flanked by a furled Russian tricolour, Stremousov blamed the failure to capture Mykolaiv for Kherson's failure to join Russia.

"As soon as we're free of the Mykolaiv group (of Ukrainian forces), who are constantly shelling Kherson city, when we take Mykolaiv region and our colleagues and citizens in Mykolaiv and Odesa regions are liberated, it will be much easier to make some decisions."

But regardless of the military situation, Kherson's de facto incorporation into Russia continues apace.

On Wednesday, Putin signed a decree allowing for residents of Kherson and the neighbouring Zaporizhzhia region to acquire fast-track Russian citizenship.

Russian banks and mobile operators have announced plans to begin operations in the region, where Ukrainian television channels have been replaced by Russian state media broadcasts.

On May 6, Andrei Turchak, head of Russia's ruling United Russia party, said on a visit to Kherson that Russia would remain in the region "forever".

The local pro-Russian administration has promised that Kherson will move to the Russian rouble, after a transition period in which both the rouble and the Ukrainian hryvnia will be accepted.

Stremousov said: "With time, we will completely abandon the dollar, completely abandon the hryvnia's dependence on the dollar and move to the rouble system, as they did in Crimea."

(Editing by Mark Trevelyan and Nick Macfie)