According to The Hill newspaper, Bolton's effort is believed to be the first time a former top adviser to President Bush has opposed a key aspect of the administration’s current foreign policy. Other officials have criticized Bush after leaving the administration, but Bolton is the first to meet with groups of GOP lawmakers to explain his opposition and possibly sway them.

Bolton addressed a joint meeting of Foreign Affairs Committee Republicans and Republican Policy Committee members last week. And he also spoke to the Conservative Opportunity Society, The Hill reports.

Bolton is critical of the agreement reached in six-party talks. North Korea has agreed to disable its main nuclear facility at Yongbyon by the end of the year. In exchange, North Korea will receive 900,000 tons of heavy fuel oil from the U.S. and other countries.

Bolton believes that trusting North Korea to abide by its promises is the wrong approach.