The Spanish-led construction consortium leading the expansion of the Panama Canal says negotiations have broken down for how to finance a $1.6 billion cost overrun and is warning that 10,000 jobs are at risk as a result. Shares of Spanish firm Sacyr SA, which leads the consortium, plunged 6.4 percent Wednesday morning in Madrid. Shares of Italy’s Impreglio SpA construction firm, which is also in the consortium, fell 2.4 percent in Milan.