Russia's natural gas giant OAO Gazprom on Tuesday threatened further gas cuts to Ukraine within hours unless agreement was reached on a debt dispute and contracts for future deliveries, AP reported Gazprom on Monday cut shipments to Ukraine by about a third and spokesman Sergei Kupriyanov said another 25-percent reduction would be imposed at 8 p.m. (1700 GMT) unless an agreement was signed. Much of the Russian gas consumed in Western Europe comes in pipelines that cross Ukraine and dispute has raised concerns that supplies to the West might be reduced. Kupriyanov on Tuesday repeated Gazprom's assurances that shipments transiting Ukraine would not be affected. But a three-day Gazprom cutoff to Ukraine in 2006 resulted in a reduction of deliveries downstream. Gazprom last month threatened a reduction to Ukraine over a US$1.5 billion (¤990 million) debt dispute, timed to coincide with Yushchenko's visit to Moscow. That cutoff was avoided by a last-minute agreement between Yushchenko and President Vladimir Putin. But documents formalizing that agreement have not been signed by Ukraine's natural gas company Naftogaz.