The Geneva talks have been closed to the media, but apparent sticking points have included verification and monitoring measures as well as Russia's opposition to US plans for missile defence facilities in eastern Europe.
They also come as Western powers are pressing Iran and North Korea to curb their nuclear programmes.
Neave Barker, Al Jazeera's correspondent in Moscow said the talks are "a sign the US and Russia have entered a new ear of co-operation".
But he added they were "also a potent message to other nations, Iran included, that may be heading down the road of nuclear proliferation".
A Russian diplomat told Reuters that a draft treaty would be ready "hopefully by early April".
Obama will host a nuclear non-proliferation summit on April 12-13 bringing together representatives from as many as 43 countries to help secure the world's loose nuclear material.
He called last year in Prague for a world without nuclear weapons and has made preventing the spread of atomic weapons a priority.
Russia and the United States currently hold some 95 per cent of the world's nuclear warheads.
US and Russian negotiators recently began negotiating to replace the 1991 Strategic Arms Reduction Treaty (Start), which expires this year.
The talks were launched after the first meeting between Obama and Dmitry Medvedev, the Russian president, last month.
Disagreements between the US and Russia also remain over how to deal with Iran's nuclear programme and the US's missile system plans in Europe.