Sancho has collected 43 caps for his country

The Trinidad and Tobago centre half has been training with the Millwall squad for the past week and has joined the club after receiving a work permit.

"He hasn't been with the club so we are able to sign him even outside the window," manager Kenny Jackett told the club's official website.

Sancho, 30, made 50 appearances for Gillingham before being released at the end of last season.