Closest of allies, but not when it comes radios.

British and U.S. military commanders for years have been told that they would soon be able to talk and share data over a joint radio network.

Despite considerable advances in tactical communications technology--particularly in software-based radio and digital encryption --interoperability on the battlefield between U.S. and U.K. forces remains years away.

In two separate technical demonstrations during the past three years, U.S. government engineers and contractors tested the compatibility between the Defense Department's joint tactical radio system and the U.K. Ministry of Defense's Bowman tactical radio network. Both tests by all accounts were successful, but the uncertain fate of the Pentagon's JTRS program could derail ongoing efforts to achieve seamless connectivity between U.S. and U.K. troops.

Representatives from the Defense Department and the Ministry of Defense signed an agreement in September 2002 to enhance battlefield interoperability via the U.K. Bowman communications system. Soon after, the JTRS program office awarded a contract to ITT Corp. of Clifton, N.J., to develop a joint tactical radio system Bowman waveform--a software application that would allow JTRS users to add the U.K. radio system into the U.S. network.

The agreement also brought into the fold the U.K.-developed Pritchell II cryptographic algorithm--an unprecedented level of technical data sharing, according to U.S. officials. The JTRS program office contracted with Harris Corp. of Melbourne, Fla., to deliver a "cryptographic equipment application" that would incorporate the U.K. algorithm on the Harris Sierra II encryption devices that are used in U.S. joint tactical radios.

A July 2004 test at the British Embassy in Washington, D.C., proved that both networks could exchange voice and data. Since then, however, the JTRS program suffered technical setbacks and delays, and the Defense Department put in place a new management structure. During the past two years, the U.S. military services have scaled back funds for future purchases of JTRS as they have poured billions of dollars into new non-JTRS combat radios that were urgently needed for the wars in Iraq and Afghanistan.

According to sources close to JTRS, Defense Department officials are still unsure on how to move forward with the U.K. joint program, even though British officials have offered steady support and have committed to funding half the cost of programming JTRS radios with the Bowman waveform.

In June 2007, the Defense Department hosted the second demonstration of JTRS-Bowman connectivity. At ITT's New Jersey facility, officials tested a VHF (very high frequency) joint tactical radio system Bowman waveform equipped with Pritchell II encryption.

"This was an important step in realizing U.S.-U.K. tactical command-and-control interoperability," said Sonja L. Hanson, a JTRS spokeswoman at the Space and Naval Warfare Systems Command.

The U.K. waveform used in the test is the Bowman "advanced digital radio," also known as ADR+. It is a derivative of the U.S. Army's single channel ground to air radio system (SINCGARS), which also is an ITT product.

"The information exchange included clear and encrypted voice, and data communications in both fixed and frequency hopping modes," Hanson said via email. The test also showed that the U.K. Pritchell II type I encryption was compatible with the U.S. Sierra II software-programmable chip.

What happens next remains uncertain. U.S. and U.K. officials were meeting in London in July to possibly begin to hash out a plan to move forward. A major hitch with which they must contend is the fragile state of the JTRS program, which faces significant delays, and even outright cancellation, in the next several years.

Current plans call for the Bowman waveform to be integrated into JTRS radios in 2012, but U.K. officials and some supporters within the Defense Department are pushing for the technology to be fast-tracked and installed in current non-JTRS software-programmable radios such as those made by ITT and Harris.

The dilemma is whether to wait five years to bring the Bowman network into JTRS or try to speed up the project and connect Bowman with non-JTRS radios, an official said.

Hanson said that the next phase of the U.S.-U.K. effort is to demonstrate information exchange between operational U.K. ADR+ and production-quality JTRS single channel handheld sets by 2010.

Both nations also are planning an interoperability demonstration with the U.S. Army's Future Combat Systems program, she said. As part of the agreement, the Defense Department and the Ministry of Defense are expected to collaborate on at least three related projects: a network planning and crypto key handling demonstration, the porting of the Bowman waveform to JTRS radios, and a study of the potential benefits of developing a Bowman HF (high frequency) and UHF (ultra high frequency) waveforms.

For the foreseeable future, however, the interoperability between U.S. and U.K. forces will not improve dramatically.

After the invasion of Iraq, the U.S. Marine Corps acquired handheld "personal role radios" for squad-level line-of-sight communications. This radio gave Marines instant interoperability with U.K. troops, who also employ the PRR. Some industry experts have criticized the use of the personal role radio because it has no secret encryption or frequency hopping features. The Marines said the PRR was only an interim system that they bought because when they first went into Iraq, most Marines lacked voice radios. The Army also was in a similar predicament in 2003, when it found that most soldiers in Iraq needed individual radios and there weren't nearly enough of them available in the inventory.

Defense Department data shows that the military services collectively owned fewer than 100,000 tactical radios in 2001. As a result of a $10 billion buying spree, the services now have nearly 590,000 radios.

The massive procurements of radios, however, has been bad news for JTRS because the services have shifted billions of dollars--that might have been spent on JTRS--to buy radios that already were in production. Just last month, the Defense Department announced contract awards of $3.5 billion to Thales Communications and $2.7 billion to Harris Corp. for single-channel handheld radios. Each contract has options that could augment Thales' orders to $9 billion and Harris' to $7 billion by 2012.

The extraordinary sums that are being spent of new radios have prompted a Government Accountability Office investigation. The agency is expected to release its findings some time in 2008.