Can we force reactions with positive delta G?
The change of the Free / Gibbs enthalpy $\Delta_{\text{R}}{}G$ consists of a contribution by reaction enthalphy $\Delta_{\text{R}}H$, and a contribution by reaction entropy, $\Delta_{\text{R}}S$:

$$ \Delta_{\text{R}}{}G = \Delta_{\text{R}}H - T \cdot \Delta_{\text{R}}S $$

Hence, the answer to your question is no.  By variation of temperature $T$, for example, a reaction previously endergonic ($\Delta_{\text{R}}{}G &gt; 0$) may become exergonic ($\Delta_{\text{R}}{}G &lt; 0$), as summarized here.