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(Pocket-lint) - Nokia and Apple are embroiled in a dispute over the size of future SIM cards. The “SIM War” centres around two different proposals submitted to the European Telecommunications Standards Institute (ETSI), the governing body that decide on these matters.

Each proposal lays out details for how the respective companies deem the “fourth form factor (4FF) UICC”, that’s "nano-SIM" to you and me, should be built.

Whoever proves to be successful, the nano-SIM will be even smaller than the micro-SIM currently used in the Apple iPhone 4 and 4S. It should, in theory, allow more room for manoeuvre under the bonnet of your smartphone, making it quicker, more powerful or simply slimmer.

Apple’s proposal sees the nano-SIM measuring in at 12.3 x 8.8mm and was actually sighted at this year’s Mobile World Congress. Nokia’s model is an even smaller 10 x 8mm.

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RIM is also getting in on the act with its nano-SIM’s dimensions being 11 x 9mm - although, if speculation is to be believed, RIM and Nokia are currently negotiating a pact that will see them (along with Motorola) collectively opposing Apple.

However, in an attempt to win over its rivals, Apple has promised royalty-free licences with regards to any patents tied to its nano-SIM design, should it prove to be successful. This is unlikely to win over Nokia, which has claimed that not only is its design more practical, but that Apple’s nano-SIM is also technically inferior.

It may simply be a matter of millimetres, but the outcome of the ETSI’s decision, set to be made later this week, could have a major impact on the power struggle between some of the mobile world’s biggest players.

Whose nano-SIM design do you favour? Tell us your thoughts.

Writing by Danny Brogan.