"It is imperative to put into action your pledge of increased, meaningful pressure against the Iranian regime," they said in a letter to Obama that called for "crippling sanctions" against Tehran "as early as this month."
Democratic Senators Evan Bayh, Bob Casey, Chuck Schumer, and Ben Cardin; Republican Senators Jon Kyl, John McCain, Johnny Isakson, and David Vitter; as well as Independent Senator Joe Lieberman signed the letter, a copy of which was obtained by AFP.
The message came as the US Senate was expected to act in the next few weeks on legislation targeting Iran with a crackdown on its gasoline imports, a unilateral step fed in part by resistance from China to new UN sanctions.
China's approach "calls into question whether it is interested in being a responsible stakeholder in the international system and does significant damage to its relationship with the United States," they said.
"We fear that Beijing's pursuit of its narrow commercial self-interest in Iran is jeopardizing the chances of reaching a diplomatic solution in the nuclear stand-off and greatly increases the risk of developments that could profoundly destabilize the Persian Gulf and global energy markets," they said.
The nine lawmakers said 2010 would be "the pivotal year" in the standoff and urged the US president "to do everything that is necessary to stop Iran's acquisition of a nuclear weapons capability in the critical months ahead."
"We abhor the possibility that military action may be necessary to solve this problem. But we have no doubt that a nuclear-armed Iran will be catastrophic for our national security," they wrote.
The lawmakers also supported Obama's plan to seek a fifth round of UN sanctions on Iran, which denies Western charges that it seek an atomic arsenal under cover of a civilian nuclear program, but warned China's "likely resistance to meaningful sanctions" could doom the effort.
The lawmakers also urged Obama to "increase American support for the human rights and peaceful aspirations of the Iranian people."
