The U.S. Army is looking into best possible options to replace Vietnam-era armored military vehicles with modern battle-ready units that are fit to perform roles in modern warfare.

Some of the vehicles in the Army's present inventory were put into service as early as 1961. Not surprisingly, in the current political climate in Washington, with an overall funding squeeze, the Army is treading carefully to find ways of funding its Armored Multi-Purpose Vehicle program.

Marked for replacement are between 2,000 and 3,000 assorted vehicles, many dubbed "battle taxis" because of their relatively light armor and potential unsuitability for some modern warfare scenarios, industry analysts said.

Congressional research data suggests the AMPV aims to replace Vietnam-era M-113 personnel carriers, still in service in a variety of support capacities in Armored Brigade Combat Teams, defense-aerospace.com said.

While M-113s no longer serve as infantry fighting vehicles, five variants of the M-113 are used as command and control vehicles, general purpose vehicles, mortar carriers, and medical treatment and evacuation vehicles. An estimated 3,000 of these M-113 variants are currently in service, defense-aerospace.com said.

The AMPV is intended to be a "vehicle integration" or non-developmental program, apparently to avoid controversy and to forestall failure in the acquisition effort.

Candidate vehicles chosen by the army will be either existing vehicles or modified existing vehicle but not vehicles to be specially designed.

With the Army said to favor a single supplier for the whole replacement program, an existing vehicle adapted to its purpose will be easier to buy than a vehicle to be developed under a modernization program.

Several of the Army's key developmental programs, including the Future Combat System, the Crusader self-propelled artillery system and the Comanche helicopter were canceled before they could be developed and fielded.

But the Army wants to delay the vehicle modernization programs by a year and raise its development costs by several hundred million dollars while it aims to replace the M113 infantry carriers by the early 2020s, Defense News said.

The Army issued a new draft request for proposals for its AMPV program, following a previous draft request issued in March.

Exactly how many vehicles will be bought remains unclear. Defense News said the Army wants to buy 2,097 AMPVs over 13 years costing roughly $1.8 million apiece. Other reports cited up to 3,000 vehicles earmarked for replacement.

The Army plans to award a five-year engineering and manufacturing development contract in May 2014 to one contractor, which will manufacture 29 vehicles for government testing, followed by a three-year low-rate initial production contract starting in 2020, Defense News said.

Money remains a problem for the Army, however, defense-aerospace.com said. "Sequestration or not, budgets are growing ever tighter, and investment is increasingly shifting from the ground forces that have fought so hard since 9/11 to the air- and sea-power that would be central against Iran or China.

"The Army will have to fight to make its case," defense-aerospace.com said.