Elementary subgroups of isotropic reductive groups

Let $G$ be a not necessarily split reductive group scheme over a commutative ring $R$ with $1$. Given a parabolic subgroup $P$ of $G$, the elementary group ${E}_P(R)$ is defined to be the subgroup of $G(R)$ generated by ${U}_P(R)$ and ${U}_{P^-}(R)$, where ${U}_P$ and ${U}_{P^-}$ are the unipotent radicals of $P$ and its opposite $P^-$, respectively. It is proved that if $G$ contains a Zariski locally split torus of rank 2, then the group ${E}_P(R) ={E}(R)$ does not depend on $P$, and, in particular, is normal in $G(R)$.