Dr Williams will make a week-long visit to Armenia, Syria and Lebanon following the US meeting, Lambeth Palace said.
A statement said his visit to Armenia was the result of an outstanding invitation from the Catholicos, His Holiness Karekin II, who heads the Armenian Apostolic Church.
His visit to Syria and Lebanon will be shorter and forms part of his continuing personal engagement with Christian churches in the Middle East and with leaders of other faiths in the region, the statement said.
The visit takes place at the invitation of the Anglican Bishop of Jerusalem, Suhail Dawani, whose diocese covers these countries, and is being arranged in collaboration with the Middle East Council of Churches.
In Syria, as well as meetings with Christian leaders and the local Anglican community, Dr Williams will meet the Grand Mufti of Syria and the country’s president, Dr Bashar Al Asad.
Dr Williams’s trip following the US meeting will begin before America’s formal response to this issue and will also make him unavailable for conciliation before the September deadline.