Or else what? By JoAnne Allen for [1] Reuters, with thanks to Jeffrey Imm:

WASHINGTON (Reuters) - Iran is supplying Iraqi insurgents with weapons technology used to kill American troops, a senior U.S. diplomat said on Wednesday, sending another warning to Iran against interfering in Iraq.

"We have picked up individuals who we believe are giving very sophisticated explosive technology to Shia insurgent groups who then use that technology to target and kill American soldiers," said Undersecretary of State Nicholas Burns.

"It's a very serious situation. And the message from the United States is, Iran should cease and desist."