"There is, strategically, a recognition that carrying something out on a specific date would be something that they would do, " said a U.S. counterterrorism official.

WSJ: Spies Piece Together al Qaeda Playbook

Those travelling on a more open schedule, or rather those who do not have a specific date pinpointed to make it up the mountain, can purchase their tickets in person at the Instituto de Cultural Nacional de Cusco located off the Plaza de Armas in Cusco, as well as the Machu Picchu Cultural Center in Aguas Calientes.

BBC: Securing tickets for Machu Picchu

They want a piece of paper, generated at a specific time and place, preferably with a date and signature on it.

FORBES: The Web Is A Thing Out Of Time

The junior minister said he could not give a specific date as his officials were still working on the plan.

BBC: European priorities for 2012/13

An EU official said Mr. Lew told Mr. Barnier the U.S. wasn't ready to sign up to a specific date for the implementation of Basel III rules on banks' higher capital buffers.

WSJ: Europe Financial Woes Dominate Talks With U.S.