The United States has new intelligence indicating Iran is reorganizing in an effort to assert its influence inside Iraq and may be behind several recent attacks, according to a senior U.S. official who spoke with CNN Monday.

The information underscores a view by Gen. David Petraeus, who assumes command of U.S. Central Command later this month, and Gen. Raymond Odierno that progress in Iraq remains fragile and that it is too soon for a major additional U.S. troop drawdown.

The senior official, who asked to remain anonymous because of the sensitivity of the intelligence, said the U.S. military had recently arrested an Iraqi general who says he was paid by Iran to derail a pending agreement that would allow U.S. troops to remain in Iraq after the end of the year.

The general was arrested a few weeks ago at the Iranian border carrying large sums of cash, according to the source. The man has known ties to the Iranian Revolutionary Guard Corps (IRGC), the U.S. official said.

The United States believes the IRGC has ties to terrorist operations and Iran's programs to develop chemical and biological weapons...