Russia may scrap controversial St Petersburg tower

* State media, officials start anti-tower campaign

* Gazprom says not backing off for now

By Denis Pinchuk and Dmitry Zhdannikov

MOSCOW, Nov 16 (Reuters) - Prime Minister Vladimir Putin, an early supporter of a controversial project to build St Petersburg's first glass skyscraper, is now expected to scrap it because of mounting opposition at home and abroad.

The 403-metre (1,322-foot) tower, intended to house offices of state-run gas giant Gazprom (GAZP.MM) by 2016, has caused an outcry among inhabitants of St Petersburg, Russian opposition parties and the U.N. cultural agency UNESCO [ID:nLN573166].

Putin has said he supports the $3 billion project in his home town as it would help the economy of the former imperial capital and revive a neglected corner of the city -- but that a decision lies with the city authorities.

Opponents say the tower would ruin the unique skyline of the city, often dubbed Russia's Venice. State media and some officials have begun to express doubts after years of support.

UNESCO has warned Russia it could exclude St Petersburg from its list of world heritage sites if the tower is built, as it would dominate the canals and baroque houses of the city founded by Tsar Peter the Great in 1703 as Russia's window on Europe.