regret [rɪ'gret] n. 遗憾；抱歉；悲叹  vt. 后悔；惋惜；哀悼  vi. 感到后悔；感到抱歉 

regret to do对要做的事遗憾；regret doing对做过的事遗憾、后悔

eg: I regret that the United States has added its voice to such protests.
我很遗憾美国也附和了这样的抗议。