Are modern U.S. embassies becoming too costly to build?

Building beautiful embassies comes at a cost.

In London, a modern glass structure nicknamed "the cube" will house the new U.S. Embassy when it opens in early 2017.

Six months into construction, however, CBS News learned the $1 billion project is already $100 million more expensive than initial estimates.

This is partly because of the unique blast-proof glass at the heart of the design, reports CBS News' Nancy Cordes. It's made in Europe and then shipped under guard to the U.S. for framing before being sent back to England for installation.

"Sometimes you have to move things, sometimes you don't," said Patrick Kennedy, U.S. State Department undersecretary for management.

The question is why this glass design is being used at all, as there were reports that the State Department's value engineering assessment team recommended using a different glass design because this one was too costly.

"I have not seen that report. I'll be glad to go look at it," Kennedy said. "However, the contract arrangements we have with the architects, the engineering and construction firm drive to a fixed price. So this is a good deal."

The State Department is responsible for the construction and maintenance of more than 200 American embassies around the world. Some of those embassies have been described as unattractive fortresses, which prompted the State Department to embrace a new initiative called "design excellence," put in place in 2009, to tailor the design of embassies to their location and the climate while maximizing safety.

In the Bush years, the State Department's building office had standard small, medium and large designs for most embassies and consulates like the buildings in Johannesburg, South Africa and Bulgaria.

Under the Obama administration, State Department officials decided the standard design didn't reflect America's culture and values. Buildings like those in Brunei and Guangzhou, China, utilize the design excellence approach.

"Just three different sizes is not how diplomacy works, it is an infinite range," Kennedy said.

Utah congressman Jason Chaffetz is a top Republican on the House government oversight committee, and he said these embassies now take longer to build.

These people live in very dangerous parts of the world, we don't have time to make sure that the building and the flowers look more pretty, we have to make sure that these people are safe and secure and can do their jobs," Chaffetz said.

He's visited new embassy sites like Port Moresby in Papua New Guinea, where a decision to expand the proposed embassy forced the State Department to scrap the entire design and start over.

The project estimate has ballooned from $50 million to $211 million, and according to an internal State Department document there has been a "termination of the current work and shuttering of the site until a new construction contract is awarded."

"That's just poor, total mismanagement from top to bottom," Chaffetz said.

Kennedy argues the State Department's money is being well spent.

"When you have a significant change in the scope of a project it is logical that the price would go up," Kennedy said.

Security, however, is also a driving concern. After the attacks in Benghazi, the State Department commissioned an internal security review. It warned the slower pace of construction could leave "more personnel exposed in inadequate facilities for longer periods of time" and found "no evidence of a... cost benefit analysis supporting this new design excellence initiative."

Grant Green, a former U.S. State Department undersecretary for management, oversaw the report.

"If it takes longer it's going to cost more, and if it costs more and takes longer it puts people at risk out there who are waiting for their embassy to be built," Green said.

Kennedy disagrees with the findings of the report.

"We have reviewed our processes and feel very, very comfortable that our use of the design initiative gets us the security we need and the functionality we need at the best possible price," he said.