The pursuit of a peace deal with the Taliban sought by the Trump administration is at risk of sliding back even farther as Tehran continues to support the terrorist network. Communications and intelligence have also claimed that the Taliban has been outsourcing more operations into Iran. Fear of a Tehran-led attack on U.S. troops in Afghanistan has begun to increase since the environment has shifted from Iran and the U.S. having the same goals for the neighboring country. Senior advisor to the U.S. Institute of Peace, Richard Olson, has commented that if Afghanistan becomes a battle ground between Iran and the U.S., a troop withdrawal from the country would be impossible.
Source: https://www.washingtontimes.com/news/2020/jan/20/iran-expands-taliban-support