Japan is to put 5 billion yen (Pounds 37 million) into CERN's large hadron collider project. The LHC is a particle accelerator which will search for the Higgs boson - the holy grail of particle physics.
The Japanese collaboration in the LHC is the first time that a non-member state has pledged money for the building of an accelerator. CERN is hopeful that other countries will follow Japan's example. Christopher Llewellyn Smith, CERN's director general said: "The scale of Japan's contribution to the LHC sets a new precedent in inter-regional scientific collaboration."
His optimism follows the cancellation of the Superconducting Supercollider project in the United States. It would have cost $12 billion (Pounds 7.7 billion), compared with the LHC's SFr2.6 billion (Pounds 1.4 billion), and it too would have searched for the Higgs boson.
With the SSC out of the way, CERN is the world capital of particle physics research, and may bring in more international partners.
A committee of the US department of energy's Office of Energy Research recommended last year that it contribute $400 million to the LHC.
This contribution is threatened by the US Congress, which has already made promises to cut the DOE budget by $10.6 billion over the next four years.
CERN is also holding talks with Russia, Canada, Israel and India, all of which may pledge money to the project.
CERN needs to raise an extra SFr500 million from outside sources to complete the LHC by 2004.
The accelerator will collide two oncoming beams of protons travelling at almost the speed of light.
Physicists hope that analysing the spray of particles thrown up by the collision will produce indications of the existence of the Higgs boson.
This elementary particle is a crucial part of the Standard Model, which describes the fundamental properties of matter. The Higgs boson explains why particles have the masses that they have.
As well as searching for the Higgs boson, it will be able to study the top quark - another elusive particle whose existence was confirmed using Fermilab's Tevatron accelerator in February of this year.
The LHC will be seven times more powerful than the Tevatron, capable of churning out enough top quarks to analyse their properties in detail.
David Saxon, chairman of the particle physics committee at the University of Glasgow, said of Japan's decision, "I am very happy. This will make a significant difference to the speed of construction of the LHC. We are looking forward to Japan's full participation."