TransCanada says its pipeline would be the safest ever built, and that the crude is no dirtier than oil currently arriving from Venezuela or parts of California.The issue became politically charged when congressional Republicans gave President Barack Obama 60 days to decide whether TransCanada should be granted the necessary permit for the pipeline to cross an international border before snaking its way 1,700 miles south to the Texas coast. Obama, saying his administration did not have enough time to study the potential environmental impacts, denied the permit in January. However, he encouraged TransCanada to reroute the northern portion of the pipeline to avoid an environmentally sensitive area of Nebraska. He also promised to expedite permitting of a southern portion of the pipeline from Cushing, Okla., to the Gulf Coast to relieve a bottleneck at the Cushing refinery. TransCanada began construction of that portion of the pipeline this summer after receiving the necessary permits. Some Texas landowners, joined by activists from outside the state, have tried through various protests to stop or slow down construction. ___ Plushnick-Masti can be followed on Twitter at https://twitter.com/RamitMastiAP .