The call comes as more experts are expected in Nigeria to help in the search, including US hostage negotiators.
Nigeria's government belatedly accepted offers of help last week from the United States, Britain, France, China and Spain amid mounting national and international outrage at its failure to rescue 276 girls abducted from a northeastern school on April 15.
Fifty-three escaped. The militants are threatening to sell the girls into slavery.
"But it is not enough for the Council to express concern ... It is now time for the council to act decisively against the Boko Haram. The cost of inaction is simply too high to contemplate."
He said targeted sanctions would send a strong message. The United States already has designated Boko Haram a foreign terrorist organisation, as has the European Union, making it illegal to contribute to the group.