for iran tonight, and here's abc's chief global affairs correspondent martha raddatz. >> reporter: tonight, amid growing tension with iran, calls of sabotage near the world's most important oil trading route. four oil tankers targeted at the entrance to the persian gulf. video showing a gash in one ship's stern at the water line, appearing like it was rammed or hit by a projectile. it comes just days after the u.s. warned commercial vessels in the region that "iran and/or its regional proxies" could target commercial sea traffic. and one week after the u.s. sent a carrier battle group and b-52 bombers to the gulf because of fears of a possible iranian attacks on u.s. forces. but there is no evidence at this point that iran was involved in the sabotage of these ships. even president trump cautious about blaming iran, although he did issue a warning. >> it's going to be a bad problem for iran if something happens. i can tell you that.