As the Pentagon formulates its 2008 budget request, it is weighing several different options for meeting its goal of developing the ability to strike targets around the world within an hour, according to congressional aides.

One option is to press forward with the concept of placing non-nuclear warheads on its submarine-launched Trident missiles. However, that idea encountered resistance from some members of Congress during the 2007 budget cycle. While there are other options under consideration that could have an easier time winning congressional approval, some of those options might require more development work, which would prevent them from being available as early as a conventional Trident missile, the aides said.

Alternatives to the conventional Trident concept include shorter range submarine-fired missiles as well as long-range rockets that could be launched from bases inside the United States other than ICBM fields, the aides said.

The Pentagon requested $127 million for work on the conventional Trident concept in 2007, but Congress provided only $25 million for prompt global purposes. The 2007 Defense Appropriations Act allocates $5 million to the National Academy of Sciences to conduct a study on possible solutions for the prompt global strike mission from the near-term solutions to long-term approaches. That study, which is due back to Congress May 15, must take into account military and political issues associated with the various options.

The remaining $20 million is designated for the U.S. Navy to spend on development work necessary for a variety of other unspecified global strike options. The service is not permitted to focus on Trident until completion of the National Academy of Science report.

The 2007 Defense Authorization Act also requires a report on the conventional Trident concept. The report, which is due Feb. 1, must be prepared in consultation with the U.S. Secretary of State, and must cover:

• Scenarios in which a conventional sea-launched ballistic missile could be employed.

• The rationale for rejecting other options for prompt global strike.

• A detailed cost analysis broken down by fiscal year.

• The adequacy of intelligence capabilities needed to support use of such weapons.

• The implications for ballistic missile proliferation if the United States were to go forward with a sea-launched conventional ballistic missile.

• The implications for the U.S. missile defense systems if other countries were to use similar systems.

• How to deal with the ambiguity caused by using the same ballistic missile for nuclear and conventional payloads.

Proponents of the conventional Trident concept say it offers a different paradigm from the use of nuclear-tipped ICBMs -- one in which the military would seek uses for the weapon, rather than hope it is never used.

While the military has a variety of assets in its arsenal that are capable of striking targets around the world, including tactical aircraft, bombers and cruise missiles, basing constraints slow the Pentagon's ability to hit a target that could move relatively quickly, according to Marine Corps Gen. James Cartwright, commander of U.S. Strategic Command.

"The difficulty here for prompt global strike is [that] the adversary may not choose to act near our bases or our patrol areas," Cartwright said during a March 29 hearing with the Senate Armed Services strategic forces subcommittee. "And if that's the case, and we're dealing with targets that are associated with weapons of mass destruction, command and control, terrorist-type leadership targets, these targets tend to be fleeting. They don't present themselves for long periods of time."

While the conventional Trident concept has received its strongest support from Republican members of Congress like Sen. Jeff Sessions (R-Ala.), chairman of the Senate Armed Services strategic forces subcommittee, the concept faces opposition from members of both major U.S. political parties.

During floor debate on the appropriations bill Aug. 3, Sen. Ted Stevens (R-Alaska), chairman of the Senate Appropriations defense subcommittee, said he is worried that the launch of a conventionally armed ballistic missile at a U.S. enemy could be misinterpreted by other countries as a launch of a nuclear warhead toward their territory.

Current intelligence and decision-making timelines are not well suited to the use of a weapon that would strike its target within an hour and could not be called off, Stevens said.

"This capability would offer the opportunity for risky, even reckless strikes, rather than deliberate, clearly thought-out action," Stevens said.

Proponents of the conventional Trident concept say that the system could be operational before the end of this decade. However, if the Pentagon believes it will not be able to overcome the opposition to the Trident concept on Capitol Hill, and is willing to wait longer to satisfy its desire for prompt global strike, it could ramp up its investment in research and development projects like the Army's Advanced Hypersonic Weapon, the congressional aides said.

The Advanced Hypersonic Weapon is envisioned as an unmanned vehicle that leaves the atmosphere briefly before flying back towards Earth like an aircraft during the majority of its flight, making it less likely that it would be mistaken for an ICBM, the aides said. The system could launch from a U.S. base in Diego Garcia in the Indian Ocean or Guam in the South Pacific.

The vehicle is envisioned as traveling 6,000 kilometers within 35 minutes, according to an Army document.

While the Army's Space and Missile Defense Command has conducted research into an Advanced Hypersonic Weapon, it has not funded the effort on a level necessary for a flight test, the aides said.

Another type of project that could be funded as an alternative to the conventional Trident to avoid confusion between the launch of an ICBM and a conventional warhead could involve using submarines to launch shorter-range ballistic missiles, the aides said.

Another option is developing a warhead that could be placed on top of a small space launch vehicle, and launching the weapon from a military base other than its ICBM fields, the aides said. However, Congress already has expressed resistance to this concept, and in 2004 directed the Pentagon to cease its work on designing weaponized payloads under the Falcon program.