We report the manipulation of a liquid plug inside a rectangular microchannel, when one of the channel walls is a deformable membrane, which adjoins another parallel microchannel. Elastocapillary flow of a driving liquid (DL) through the adjoining microchannel, when approaches the plug, tries to pull the membrane near the plug, which is initially deflected into the plug, towards the DL. The plug is transported due to a differential pressure that develops across the plug owing to the increase in the radius of curvature of the trailing meniscus of the plug. A theoretical model is proposed to predict the plug velocity, which depends on a parameter J and plug length L. The predictions of the theoretical model show good agreement with experimental data. The dynamic behaviour of the plug and DL is presented and discussed. © 2015 AIP Publishing LLC.