Media report states that the US government regards North Korea’s attack on the Cheonan as a violation of international law and aggression against an ally, so apart from a joint response with South Korea, Washington is considering taking sanctions on its own. The sanctions would be on finance as the U.S. is apparently minded to freeze again North Korea’s accounts in the Macau-based Banco Delta Asia, which were first locked in 2005.
Other reason may be the US want to isolate North Korea by imposing sanctions against trade partners like Syria, which is suspected of buying weapons from the North. U.S. intelligence agencies believe that the attack on the Cheonan was likely carried out at direct orders of leader Kim Jong-il, the New York Times said Sunday.
US firmly believe that the Cheonan sinking was the handiwork of North Korea and the investigation also points towards that. Thus U.S. is adamant to put hard restrictions on North Korea.