U.S. tightens grip on Iran's financial system  WASHINGTON Mon
Jan 23, 2012 5:01pm EST  WASHINGTON (Reuters) - The United
States on Monday sought to tighten the financial screws on Iran
by imposing sanctions on the country's third-largest bank for
allegedly helping Tehran develop its nuclear program.       Bank
Tejarat was penalized for providing financial services to the
Islamic Republic of Iran Shipping Lines and other entities
already sanctioned for their involvement with the country's
nuclear program.  The action "strikes at one of Iran's few
remaining access points to the international financial system,"
Cohen said. Twenty-three Iranian-linked firms have been
sanctioned by the United States, a list that now includes all of
the largest state-owned banks.  Washington also accused Bank
Tejarat of indirectly supporting the activities of Iran's
Revolutionary Guard.   The aim is to starve Iran of revenues
needed to develop nuclear weapons without disrupting jittery oil
markets and impeding the U.S. economic rec