Dozens of US nuclear weapons stored at a Turkish air base near Syria are at risk of being captured by "terrorists or other hostile forces," a Washington think tank claimed Monday.
Critics have long been alarmed by America's estimated stockpile of about 50 nuclear bombs at Incirlik in southern Turkey, just 70 miles (110 kilometers) from the border with war-torn Syria.
Incirlik is a vital base for the US-led coalition fighting the Islamic State group in Iraq and Syria, with the strategically located facility affording drones and warplanes fast access to IS targets.
But the Pentagon in March ordered families of US troops and civilian personnel stationed in southern Turkey to quit the region due to security fears.
While the Pentagon does not discuss where it stores nuclear assets, the bombs are believed to be kept at Incirlik as a deterrent to Russia and to demonstrate America's commitment to NATO, the 28-member military alliance that includes Turkey.
The Incirlik nuke issue has been the subject of renewed debate in the United States since the coup attempt.
"While we've avoided disaster so far, we have ample evidence that the security of US nuclear weapons stored in Turkey can change literally overnight," Steve Andreasen, director for defense policy and arms control on the White House National Security Council staff from 1993 to 2001, wrote in an opinion piece in the Los Angeles Times last week.
The Incirlik concerns were highlighted as part of a broader paper into the Pentagon's nuclear modernization program, through which the United States would spend hundreds of billions of dollars to update its atomic arsenal.
The authors argue that a particular type of bomb -- the B61 gravity bomb -- should be immediately removed from Europe, where 180 of the weapons are kept in Belgium, Italy, Germany, the Netherlands and Turkey.