* U.S. asks others to block Quds force activities
* U.S. has sanctioned 10 firms for Iran energy trade
* U.S. sees slowdown in China investment in Iran energy
(Recasts with new quotes, 10 companies sanctioned, details)
By Susan Cornwell
WASHINGTON, Oct 13 The United States is
considering more sanctions on Iran's central bank to "ratchet
up the pressure" on Tehran after an alleged plot to kill the
Saudi ambassador to the United States, a senior Treasury
official said on Thursday.
Treasury Undersecretary David Cohen said the Obama
administration's efforts to tighten the financial
and commercial screws on Iran were paying off, but other
approaches were also being considered.
"We are looking very actively at the possibility of
designating the central bank of Iran, as well as taking other
actions in response to this plot" and Iran's nuclear program,
he told a Senate committee.
"We're looking quite intensively at how to ratchet up the
pressure," Cohen said.
Cohen and Undersecretary of State Wendy Sherman appeared
before the Senate Banking Committee two days after U.S.
authorities announced they had uncovered a plot by two men
linked to Iran's security agencies to assassinate Saudi
Ambassador Adel al-Jubier.
One man, Manssor Arbabsiar, was arrested last month while
the other was believed to be in Iran.
Iran denied the charges and expressed outrage at the
Cohen said the latest allegations were a reminder that the
threat from Iran was not limited to its nuclear ambitions.
Iran already faces U.S. and international sanctions over
its nuclear program. Iran says its nuclear work is peaceful and
aimed at generating electricity.
Sherman said Washington was taking "robust diplomatic
action to hold Iran accountable for this plot," by asking
countries round the globe to stop any activities by the Quds
Force, an arm of Iran's Islamic Revolutionary Guard Corps.
U.S. officials, including Senate Intelligence Committee
Chairwoman Dianne Feinstein, have said they believe the Quds
Force was involved in the plot against the Saudi ambassador.
U.S. financial institutions are already generally
prohibited from doing business with any bank in Iran, including
the central bank. Cohen said more U.S. action against the
central bank, if it had international support, could further
The United States has pressed hard for governments and
companies to stop dealing with Iran. Sanctions on the financial
and energy sectors, which were broadened last year, have made
it harder to trade.
IRAN HAS TROUBLE GETTING OILFIELD INVESTMENT
Some U.S. lawmakers want to pass a bill to refine the
sanctions on Iran. Cohen said the administration would welcome
this, although he said the existing tools were "enormously"
Iran was increasingly unable to attract foreign investment
in its oil fields and could lose $14 billion a year in oil
revenues through 2016, Cohen said.
Since September 2010, the State Department has sanctioned
10 foreign companies for doing business with Iran's energy
sector, Sherman said.
The U.S. has also persuaded multinational energy firms such
as Shell, Statoil, ENI, Total and INPEX "to withdraw from all
significant activity in Iran," Sherman said. These companies
had "forfeited billions of dollars of investments," she said.
Republican Senator Richard Shelby said the administration
could do a better job in enforcing sanctions law.
"One problem is that the White House and the State
Department have carefully managed to avoid labeling any major
Russian, Chinese, or other U.S. trading partner's companies as
violators of U.S.-mandated sanctions," Shelby said.
Cohen replied that Russia was not a "significant problem"
in financial dealings with Iran, while Sherman said there was a
"slowdown" in Chinese involvement in Iran's energy sector.
"It is our belief from what we know that in fact Chinese
companies have not finalized any new upstream investment or
refinery construction projects" since new U.S. sanctions became
law a year ago, Sherman said.
(Editing by Cynthia Osterman)