KABUL (Reuters) - The United States and Afghanistan have agreed a final version of a security pact that will help determine whether US troops remain in Afghanistan beyond 2014, an Afghan spokesman said on Tuesday.

The last-minute deal was reached two days before Afghanistan's elite gathers to vote on the pact. The spokesman said US President Barack Obama had agreed to write a letter to the Afghan people acknowledging mistakes made during the "war on terror" and the suffering of the Afghan people.

The letter is to be presented along with the draft at the meeting of tribal elders that is due to start on Thursday and run for several days.