They cite such nations as Pakistan, which provides much of the intelligence and manpower needed to go after armed organisations bent on attacking US interests.
Then there are allies in Central Asia that provide basing and overflight rights for the US military. In the case of Djibouti, cooperation is needed to secure ports of entry used by people described by the US as terrorists going to and from the Horn of Africa.
Officials from the Bush administration often cite 11 September 2001 as the day the world changed. One of the changes included relaxing arms-export regulations in an effort to curry favour with countries deemed strategically important in the fight against al-Qaida and other jihadist groups, some experts said.
"Certainly the day after the 9/11 bombing attacks, we saw the Bush administration ask for a blanket lifting of restrictions on arms-export controls," said Rachel Stohl, a senior analyst at the Center for Defence Information (CDI), a Washington thinktank.
This constitutes a reversal of a long-standing US policy, Stohl wrote in a recent CDI report.
Once Taliban's sponsor, Pakistan
today is an indispensable US ally
"The Bush administration has expressed a willingness to provide weapons to countries that in the past have been criticised for human-rights violations, lack of democracy, and even support of terrorism," she said.
In the wake of the 9/11 attacks, President George Bush waived sanctions established under the Arms Export Control Act against India, Pakistan and several other countries.
Bush said the sanctions were not in the "national security interests of the United States", a move some experts said sent a message that the US would lift penalties on states that provided assistance in the "war on terrorism".
"We are definitely seeing, since the war on terrorism, this ramping up in arms export, especially to new allies in the campaign," said Frida Berrigan, deputy director of the Arms Trade Project at the World Policy Institute.
Congress passed the Arms Export Control Act in 1976 to establish a licensing system for the commercial sale of arms to foreign governments.
"That is the yardstick by which all arms exports are supposed to be measured, but that yardstick isn't being used," Berrigan said.
"We are definitely seeing, since the war on terrorism, this ramping up in arms export, especially to new allies in the campaign"
Deputy Director of the Arms Trade Project at the World
Policy Institute, Washington DC
Prior to September 11, US sanctions greatly diminished weapons sales to several countries now receiving such aid, according to a recent CDI report.
Pakistan, India, Armenia, Tajikistan and Yugoslavia have all had their sanctions lifted and are all considered allies in the US war on terrorism.
In the case of Pakistan, the need to secure its help in confronting Taliban and al-Qaida fighters in neighbouring Afghanistan was of such strategic importance, that past transgressions involving nuclear proliferation were overlooked, experts say.
"We needed to woo them, we needed to get them back in the fold," said Matt Schroeder, project manager of the Arms Sales Monitoring Project at the Federation of American Scientists.
By most accounts, Pakistan's cooperation in the "war on terror" has been significant. Such assistance was rewarded with $75 million in 2002 for the purchase of US-made weapons and more than $200 million in 2003 for such purposes, according to the CDI report.
Pakistan was recently given "major non-NATO ally status", making it eligible to receive increased levels of US military equipment.
Several countries in Central Asia, including Tajikistan, Uzbekistan, Azerbaijan and Armenia, received substantial US funding in the two years after 9/11 for weapons or military training. All had been denied such assistance before the attacks, yet subsequently all were recruited as allies in the "war on terrorism".
Some, as in the case of Turkmenistan, provided overflight rights, while others such as Azerbaijan were given millions of dollars for "specialised training and equipment to prevent and respond to terrorist incidents".
Central Asian nations are getting
rewards for security cooperation
Many of these countries have troubling political histories involving military coups, civil wars and various inter-state conflicts.
Some arms-control experts worry about the difficulty of ensuring that weapons sold to such countries aren't diverted into the hands of terrorist groups or other private militias.
"A lot of the mechanisms that are in place to control and safeguard US weapons from being misused aren't enforced," Berrigan says.
End-user agreements, designed to ensure that weapons shipments reach their intended destinations, have been broken in the past, she said, and the offending nations often go unpunished.
"We are sort of looking the other way when they violate end-user agreements," she says.
With the rise of illegal arms trafficking, experts fear the possibility that US arms shipments will be bought and rerouted by third-party middlemen to free-lance terrorists seeking high-tech weaponry.
"The risk of diversion is significant," Stohl said.
Experts say the risk of diversion
of US arms exports is significant
Stohl said the Bush policy of expanding arms sales to countries with unstable political climates is "counter-intuitive" in the post-9/11 environment.
Some analysts also question the practice of lifting arms-export sanctions against countries often criticised for human-rights violations.
Several countries in Central Asia condemned for human-rights abuses by the State Department have benefited from US military assistance in exchange for support in the "war on terrorism", experts say.
The sale of small arms, in particular, has allowed certain countries to crack down on political dissent from opposition groups, Berrigan said.
"These are the sort of weapons that are used to perpetrate human-rights abuses," she said.