GENEVA — The largest machine ever made to explore the world's tiniest particles will be launched next month with an initial attempt to fire beams around a 17-mile circular tube, the European Laboratory for Particle Physics said Thursday.

Scientists from around the world have been waiting eagerly to run experiments on the 4 billion Swiss franc ($3.8 billion) Large Hadron Collider, under construction since 2003 and in planning for years before that.

The new Geneva collider will recreate the rapidly changing conditions in the universe a split second after the so-called Big Bang. It will be the closest that scientists have yet come to the event that they theorize was the beginning of the universe. They hope the new equipment will enable them to study particles and forces as yet unobserved.

"We're finishing a marathon with a sprint," said project leader Lyn Evans. "It's been a long haul, and we're all eager to get the LHC research program under way."

Collisions of particles to see what happens will take some time longer, but they should be occurring this year. The first beam will travel in a clockwise direction on Sept. 10, a laboratory statement said. When beams are stable in both directions, they will be steered into collision.

Then the laboratory, known as CERN for its old French initials, will start stepping up the power with the hope of reaching a new threshold of energy by the end of this year. Further step ups are planned until the equipment runs at full power, probably by 2010.

The collider, installed in a tunnel under the Swiss and French border, has massive detectors filling cathedral-sized rooms at intervals along the tube. They will record the shower of particles that result from collisions so that they can be analyzed by powerful computers.

An innovation will be the use of 1,600 superconducting magnets to guide the beams traveling at the speed of light around the machine, which is being cooled to near absolute zero degrees for maximum efficiency.

The money to construct the collider has come from the 20 member states of CERN plus observer countries like the United States, which alone has contributed $531 million.

But overall the project is costing much more - an estimated 10 billion francs (dollars) - taking into account what universities and others are spending on experiments and other outlays, said CERN spokeswoman Renilde Vanden Broeck.

Much of the interest in the project has come from the United States since Congress in 1993 halted construction of a machine that would have been even bigger - the proposed Superconducting Super Collider in Texas.

Of the 9,000 scientists planning to work with the LHC, the largest group - 1,260 - is from the United States.