International Business Machines Corp said yesterday that its joint venture with Nokia that will enable travelling executives to change plane reservations using mobile phones has yet to be proven and has to go through customer tests first.

In an announcement from the US earlier yesterday, IBM announced a wireless travel reservation service which it hoped to launch by the end of 1999.

Mr Mark Bregman, IBM's General Manager for Pervasive Computing, told a press conference at the annual CeBIT technology trade fair that the scheme was still in the evaluation stage. A traveller using the wireless reservation system could make new travel arrangements as plans change - in an office, a hotel, or the back of a taxi on the way to an airport - using a new generation of Nokia 7110 "smartphones".