By Humeyra Pamuk, Simon Lewis and Matt SpetalnickWASHINGTON, Sept 12 (Reuters) - A lightning offensive by the Iran-aligned Houthis has put the militants in a position to control a crucial Middle East waterway, creating a major new problem for U.S. Analysis-Houthi advance in Yemen puts U.S. Key points and original sources are listed below.

• By Humeyra Pamuk, Simon Lewis and Matt SpetalnickWASHINGTON, Sept 12 (Reuters) - A lightning offensive by the Iran-aligned Houthis has put the militants in a position to control a crucial Middle East waterway, creating a major new problem for U.S. President Do...S1

• Analysis-Houthi advance in Yemen puts U.S. in a new bindS2