The new Queensferry Crossing will open to traffic on August 30, ministers have announced.

It will then close a few days later to allow 50,000 people to take part in a "once-in-a-lifetime chance" to walk across the bridge before it becomes a motorway with no pedestrian access.

The £1.35 billion bridge across the Forth was due to open last December but its completion was delayed by adverse weather conditions.

Holyrood Economy Secretary Keith Brown met with workers from the Forth Replacement Crossing (FRC) project and veterans of the construction of the Forth Road Bridge at the Queensferry Crossing on Tuesday.

He said: "It is fitting to be able to make this announcement alongside some of those who built the Forth Road Bridge and those who are building the Queensferry Crossing.

"What is being achieved on the Forth today, like what was achieved 53 years ago, is a testament to the expertise and the endeavour of those who have designed and built these bridges.

"I am very pleased to be able to confirm the Queensferry Crossing will open on August 30.

"The bridge will be used by vehicles up to September 1 before closing to allow the public the chance to walk across it as part of the Queensferry Crossing Experience on September 2 and 3.

"This Queensferry Crossing Experience will allow for up to 50,000 people to have the once-in-a-lifetime chance to walk across the Queensferry Crossing before it becomes a motorway with no pedestrian access.

"In order to manage access to the bridge, there will be a ballot to decide who will have this unique opportunity to be one of the 50,000 people.

"I would encourage as many people as possible to enter and take part."

He added: "This marks the beginning of the end of a 10-year process for this project.

"Starting with the early Forth Crossing studies, the Act of Parliament, design, procurement, through to work beginning on site in August 2011.

"Excitement and anticipation will build in the months ahead as people prepare to walk and drive over this bridge for the first time."

The ballot opened at 9am on June 20 and closes at noon on July 5.

To enter the ballot, people should visit the Queensferry Crossing Experience website at www.queensferrycrossingexperience.com

Michael Martin, project director for the consortium building the Queensferry Crossing, Forth Crossing Bridge Constructors (FCBC), said: "The Queensferry Crossing is one of the world's great bridges.

"It's the largest bridge of its type and its fast-track design and construction has presented many challenges.

"The safety of our workforce, who have worked relentlessly through the hostile weather conditions in the Forth estuary to deliver the earliest completion of this project, has always been our number-one priority and it will continue to be so as we move towards the completion of the project."