Swiss watchmaker Omega has signed a £25m ($47.1m) deal naming it official timekeeper of London's 2012 Olympics.
The deal marks Omega's 25th stint as timekeeper of the Games
Organisers said the latest deal means 60% of the major sponsors of the 2012 Games were already signed up.
McDonalds, Visa, Coca-Cola, GE and Atos Origin are the big-name international backers named so far.
The news came a day it was announced sales of National Lottery scratchcards to raise funds for the 2012 event had reached £16.3m, £2.3m ahead of target.
The Lottery is expected to put up to £1.5bn towards the cost of the London Games, half of which will come from specialist games such as Go For Gold and Win Gold.
Omega is already signed up to be official timekeeper of the 2008 Beijing Games and performed the same function at the recent Winter Olympics in Turin.
The 2012 event will mark its 25th stint as timekeeper of the sporting Games - an earlier occasion having been one of London's earlier turns to play host to the Olympics, in 1948.
International Olympics Committee (IOC) organisers have refused to be drawn on how much money they hope to raise from sponsorship deals.
However, when journalists asked whether its target was around the £1bn mark, IOC marketing commission chairman Gerhard Heiberg said: "If we end up like you are indicating, we will be happy."
Organisers added they were looking for a further four to six big names to join the current top-tier of sponsors for the London event. The IOC will launch its search for local sponsorship next month.