The ratification vote came the same day that Secretary of State Colin Powell was holding talks with Ivanov aimed at paving the way for a smooth summit between President Vladimir Putin and President Bush scheduled in several weeks.
The vote removes one potential source of friction at those talks, which already must deal with the contentious issues of missile defense, arms sales to Iran and postwar Iraq.
The Duma had dragged its feet on ratification of the treaty because of the U.S.-led war in Iraq, which Russia opposed.
Putin used a meeting Tuesday with Duma leaders to urge lawmakers to ratify the treaty, calling it an "important document in the sphere of strategic stability."
"Its provisions enable us to develop our strategic forces at a level of reasonable sufficiency, in line with the country's economic capabilities and the dynamics of the military and political situation in the world," Putin said, according to Russian news agencies.
After considering the treaty in closed-door debate, the Duma, the lower house of parliament, voted 294 in favor of the treaty while 134 voted against it.
The U.S. Senate already has approved the accord, formally called the Moscow Treaty.
Russia's upper house of parliament, the Federation Council, must still approve the treaty in order for the ratification to take effect, but that vote is expected to be a formality.
The Moscow Treaty calls on Russia and the United States to cut their strategic nuclear arsenals by about two-thirds, to 1,700 to 2,200 warheads, by 2012.
The treaty allows each country to stockpile the warheads, which are to be taken off-duty, contrary to Russia's initial push for their destruction. The cash-strapped Russian military cannot afford to maintain nuclear arsenals on par with the United States.
Hard-line opponents of the treaty in Russia called it treacherous.
Communist lawmaker Nikolai Kolomeitsev on Wednesday proposed to take the treaty ratification off the agenda, saying that it would lead to the "catastrophic decline of Russia's security".
The treaty supporters say that it would allow Russia to retain its aging Soviet-era missiles equipped with multiple nuclear warheads, which form the core of the nation's nuclear arsenals and were to be scrapped under the earlier START II arms reduction treaty, which Russia has never ratified.
In the draft ratification document, Duma urged the government to provide more funds to maintain the nation's nuclear forces on a "level that would guarantee the deterrence against any aggression."
Pointing at the treaty's provision that allows each party to opt out of it on three months' notice, the Duma said that Russia can use this right in case of "significant buildup in strategic offensive weapons of some nation or a group of nations" or the deployment of a missile defense system "capable of significantly reducing the efficiency of Russia's strategic nuclear forces."
Although it didn't name the United States, the provision was a clear reference to the proposed U.S. missile shield. Washington says that deploying missile defenses is not aimed against Russia but many Russian lawmakers and military officials voiced concern that the deployment could erode the deterrent value of Russia's nuclear arsenals.
After years of Russia's fervent protests against U.S. missile defense plans, Putin reacted calmly when the United States withdrew from the 1972 Anti-Ballistic Missile Treaty barring the deployment of such a missile shield, saying that the move was a mistake but not a threat to Russia.
At their talks June 1, Putin hopes to strike a deal with Mr. Bush for cooperation in missile defense systems.
Other issues include postwar arrangements in Iraq and sales of Iraqi oil under a U.N. program due to expire early next month.
Russian technology sales to Iran will also be on the agenda. The Russians are resisting ending the sales despite urgent appeals by the Bush administration that the technology adds significantly to Iran's nuclear weapons goals.
The Moscow Treaty and missile defense are part of a broad rethinking of U.S. nuclear strategy within the Bush administration.
Congress is considering lifting a ban on low-yield nuclear weapons and funding research into bunker-busting earth-penetrating nuclear bombs. Late last month, for the first time in 14 years, a U.S. lab created a plutonium "pit," the core of a nuclear device.
The Pentagon, meanwhile, is conducting conceptual discussions on what circumstances might require an end to the U.S. moratorium on nuclear tests.