LONDON, England (AFP) — British authorities insisted today that Olympic security would not be compromised after having to draft in an extra 3,500 troops because a private security firm failed to provide enough guards.

The embarrassing development adds to worries about Britain’s preparations for the London Games, which officially open on July 27, as fresh problems also emerged with transport and border security for the event.

Home Secretary Theresa May made an urgent statement to lawmakers confirming that private contractor G4S could not supply all the security staff it had promised due to recruitment and training problems.

“Let me reiterate that there is no question of Olympic security being compromised,” the interior minister told lawmakers.

She said the government had built in contingency plans to what is Britain’s largest security operation since World War II but that “concerns have arisen about the ability of G4S to deliver the required number of guards”.

“We have now agreed it would be prudent to deploy additional military support to provide greater reassurance,” she said.

May said she was confident the government would be able to stick to its security budget for the Games, which stands at (US$877 million.

A total of 17,000 troops will now be involved in securing the Olympics.