King Abdullah of Saudi Arabia suggested the Obama administration insert electronic micro-chips into Guantanamo Bay detainees to track their movements on release, a State Department cable released by WikiLeaks showed.
"This was done with horses and falcons, the King said," according to the cable. The king suggested Bluetooth technology could be used to keep tabs on the men, according to press reports.
The king raised the idea in a March 2009 meeting with White House counterterrorism official John Brennan in Riyadh, where the men had discussed a range of security issues including closure of the US prison at Guantanamo Bay, according to ABC News.
"I've just thought of something," the king said to Mr Brennan, suggesting the chips.
Mr Brennan responded by saying: "Horses don't have good lawyers," adding the idea would likely face severe opposition from civil libertarians in the United States.
He assured the king, however, that "keeping track of detainees was an extremely important issue".
The US government said it would tighten security after WikiLeaks released more than 250,000 US diplomatic cables that include candid views of foreign leaders and blunt assessments of security threats.