The US Missile Defense Agency (MDA) has advanced in developing an anti-ballistic missile defense system but continues to be beset by testing delays and acquisition problems, the US Government Accountability Office (GAO) said in an annual report on the program on Wednesday.

"MDA did not conduct six planned flight tests in fiscal year 2014, and it has been unable to conduct all of its planned tests since fiscal year 2010 because its test plan is ambitious and success-oriented," GAO said.

The situation, GAO explained, "makes it difficult to adjust the schedule if necessary and results in frequent changes and disruptions to its test plan."

While GAO noted two intercept tests demonstrated an increased capability, failure to carry out the other six tests reduced the MDA"s ability to learn from the tests and any potential mistakes.

Despite not carrying out the tests, GAO said, the MDA continued with acquisition which could lead to delays and unnecessary cost expenditures.

The MDA has continued to deliver elements of the missile defense system despite testing delays and failure, explaining that "without completing planned testing, MDA is delaying or foregoing the full breadth and depth of knowledge it planned to have attained prior to the delivery of its assets."

"MDA is still allowing production to get ahead of testing - a practice which has consistently led to cost and schedule growth as well as performance problems in the past," GAO said.

Since 2002, MDA has spent $105 billion developing a missile defense system. The Agency said it plans to spend an additional $38 billion between 2014 and 2019.

Ballistic missile defense combines space based sensors, ground and sea based radars and missile interceptors, and a command and control centre designed to target short, medium and intercontinental ballistic missiles.

The United States plans to build missile defense systems on its west coast to defend against attacks originating from Asia as well as a system in Europe under the NATO umbrella.

The move is viewed in Russia as a threat to its national security and nuclear deterrence capabilities, while the United States and NATO claim their ballistic missile defense system is aimed at intercepting a small number of missiles launched from countries like Iran and North Korea, and is not directed against Moscow.

Source: Sputnik News