  Our main aim in this paper is to constrain the effective field theory
describing the top quark couplings through the $e^{-} e^{+} \rightarrow t
\bar{t}+$jet process. The analysis is carried out considering two different
center-of-mass energies of 500 and 3000 GeV including a realistic simulation of
the detector response and the main sources of background processes. The
expected limits at 95\% CL are derived on the new physics couplings such as $t
\bar t \gamma$, $t \bar t Z$, and $t \bar t g$ for each benchmark scenario
using the dileptonic $t \bar{t}$ final state. We show that the 95\% CL limits
on dimensionless Wilson coefficients $\bar{c}_i$ considered in this analysis
could be probed down to $10^{-4}$.

High Energy Physics - Phenomenology