The United States said Monday that a deal was possible at Iran nuclear talks in Vienna, but that an agreement had to be completed urgently as Tehran advances its nuclear capabilities. “A deal that addresses all sides’ core concerns is in sight, but if it is not reached in the coming weeks, Iran’s ongoing nuclear advances will make it impossible for us to return to the JCPOA,” a State Department spokesperson said, referring to the 2015 framework agreement. The talks will resume in Vienna on Tuesday after negotiators in recent weeks have cited progress in seeking to revive the 2015 accord that w…