Former Secretary of State Condoleezza Rice called Tuesday on the US Congress to ratify the landmark START arms control treaty with Russia, which she called "integral" to America's security.

"A modern but smaller nuclear arsenal and increasingly sophisticated defenses are the right bases for US nuclear security (and that of our allies) going forward," wrote Rice in the Wall Street Journal newspaper.

If the "right commitments and understandings" are in place, she said, the treaty "deserves bipartisan support -- whether in the lame-duck session or next year."

Republicans in the US Senate have been holding up action on the new Strategic Arms Reduction Treaty, which President Barack Obama wants ratified by the end of the year.

Number-two Senate Republican Jon Kyl has suggested that there is insufficient time remaining in the current session of Congress to debate the treaty, which he has said lawmakers might block until March.

Rice expressed support for the deal, and said it is also time to look at ways to end proliferation in other countries to safeguard America's security.

"After this treaty, our focus must be on stopping dangerous proliferators -- not on further reductions in the US and Russian strategic arsenals, which are really no threat to each other or to international stability," she said.

Rice served for the eight years of the George W. Bush administration as national security adviser and secretary of state.

She added that the prospect of "loose nukes in the hands of a terrorist... should give our governments a reason to work together beyond New START and address the threat from tactical nuclear weapons, which are smaller and more dispersed, and therefore harder to monitor and control."

Rice, who before joining the Bush administration worked in academia as a Russia expert, currently teaches political economy at Stanford University in California.

Last week, five former US secretaries of state called for ratification of START, saying in a newspaper opinion piece that the treaty would continue a decades-long effort to make the world safer.

The article, which appeared in the Washington Post, was signed by secretaries of state for the past five Republican presidents: Henry Kissinger, George Shultz, James Baker, Lawrence Eagleburger and Colin Powell.