The United States has sent top officials to China, Russia and Turkey to brief counterparts there about the alleged Iranian plot to kill the Saudi ambassador in Washington, a US official said Thursday.

The "briefing teams" include officials from various government agencies who "are well-versed in how this case came forward and on the details," the senior State Department official told reporters on condition of anonymity.

The official said Washington proposed sending the teams to Russia and China -- which along with the United States are permament members of the UN Security Council -- as well as to Turkey, which is a US ally and neighbor of Iran.

The decision to send the teams, which could travel to other countries, comes as the State Department ordered all its embassies to mobilize their host countries against Iran over the alleged plot.

State Department spokeswoman Victoria Nuland said Wednesday that several countries did not apply sanctions against Iran as strongly as they might.

On Thursday, Nuland said "the question ahead of us is what further steps we can take in the UN and those consultations continue with our UN Security Council partners."

Nuland added: "Our message has been very clear that we think that Iran should be held to account. So I think it's premature to say what the Security Council might be prepared to do, but we're continuing to work on that."