The United States is reportedly considering unilateral financial sanctions on North Korea following Pyongyang’s sinking of the Cheonan naval ship.

In an interview with Japan’s Kyodo News Friday, U.S. Assistant Secretary of State Philip Crowley said that following the sinking of the Cheonan, the U.S. is reviewing a range of options in order to deliver a message to North Korea.

Crowley said Washington has been able to use financial steps to apply pressure on Pyongyang before, and the U.S. is always looking for ways it can influence the North's behavior.

Crowley’s remarks come as Reuters quoted sources familiar with Washington-Pyongyang relations as saying that the U.S. is considering freezing the North’s overseas assets.

According to the sources, the North’s illegal funds abroad will be subject to U.S. financial sanctions. The sources added that the Barack Obama administration believes the U.S. blacklisting of Macao's Banco Delta Asia in 2005 was an appropriate way to pressure the North. The bank was accused of engaging in money laundering for the North’s government.

The sources also said that Washington’s hard-line policies against the North will likely support efforts to get the North to return to the six-way nuclear talks.