By Supantha Mukherjee and Alexander Marrow

STOCKHOLM/MOSCOW (Reuters) - When telecoms gear makers Nokia and Ericsson leave Russia at the end of the year, their departure could steadily cripple the country's mobile networks over the long-term, setting off a deterioration in communication for everyday Russians.

Five senior telecoms executives and other industry sources said Russian mobile phone users will likely experience slower downloads and uploads, more dropped calls, calls that won't connect, and longer outages as operators lose the ability to upgrade or patch software, and battle over dwindling spare parts inventories.

Ericsson and Nokia, which together account for a large share of the telecoms equipment market and close to 50% in terms of base stations in Russia, make everything from the telecom antennas to the hardware that connects optical fiber carrying digital signals.

They also provide crucial software that enables different parts of the network to function together.

"We are working towards the end of the year and that's when all exemptions (from sanctions) expire," Ericsson's finance chief Carl Mellander told Reuters. Ericsson received exemptions to sanctions from Swedish authorities.

Nokia CEO Pekka Lundmark echoed that sentiment in a interview: "Our exit will be complete. We are not going to deliver anything to Russia."

Russia's economy has so far weathered sanctions and export controls put in place by governments after Moscow sent tens of thousands of troops into Ukraine, but the impending withdrawal of Nokia and Ericsson could have a more profound impact on Russian daily life, eventually making difficult something as simple as a phone call.

Russia's digital ministry did not respond to requests for comment, but this week Maksut Shadaev, minister of communications and mass media, said four telecoms operators were signing contracts to spend more than 100 billion roubles ($1.45 billion) on Russian-made equipment.