Western diplomats and energy analysts say it is unreasonable to expect Beijing to significantly cut Iran imports in the short term because of its high dependence on them.
It remains unclear whether Washington will accept the import drop-off from early this year as reason for an exemption.
Mark Dubowitz, executive director at the Foundation for Defense of Democracies, a Washington think tank that has pushed for more sanctions against Iran, said the Obama administration is likely concerned about granting China a waiver based on earlier cuts at a time when Iranian crude imports return to previous levels.
"The administration may, however, decide to move ahead with the waiver to avoid a political fight with Beijing," he said.
Chinese Foreign Ministry spokesman Hong Lei reiterated China's opposition to U.S. sanctions at a daily news briefing on Thursday. "China's import of oil from Iran is completely fair and reasonable and does not hurt third parties or the international community," Mr. Hong said.