By withholding material the US gives away the one argument which could force the Ukraine to accept.
The Ukraine already said they fight on with outside support or not.
RT or Russia Today does not qualify as a trustworthy source by the way.
If Russia agrees to a complete ceasefire on line of control, Ukraine would have no choice but to agree with it. Zelensky might be talking tough before the meeting but he is hoping a complete ceasefire would come in action.
Russia too have interest in a ceasefire as that may enable them to get back to world market. The war is about to ruin their economy. This might stop the Putin's dream of having a land border to Transnistria but Ukraine like always would still be up for grab anytime. One way or other.