Russia is ready to help the United States fight nuclear proliferation in the Mideast and the Korean Peninsula, including with regimes "secretly" seeking atomic arms, President Dmitry Medvedev said Monday.

Medvedev made the remarks after meeting in Moscow with US President Barack Obama, who has sought Russian help in dealing with Iran's and North Korea's nuclear programmes.

"The world situation is not getting better but worse," Medvedev said at a joint press conference with Obama in the Kremlin.

"This is connected to the appearance of new nuclear players, many of whom have not signed onto the nuclear club, but who are either dreaming of this and doing it openly, or secretly preparing for it," he added.

"There are certain regions where the mere presence of nuclear weapons may create colossal problems, and precisely in this area we must work with our American partners with maximum closeness."

Medvedev did not name Iran or North Korea but said: "What happens with the situation in the Mideast, what happens with the situation on the Korean Peninsula, will affect... the shared situation in the world."

Last month, Russia joined the United States and China in supporting a strict United Nations Security Council resolution penalizing North Korea for its recent test of an atomic bomb.

On Iran, however, Russia has been reluctant to impose tougher sanctions on Tehran over its alleged nuclear weapons programme and is in fact building a nuclear power plant in Iran despite US criticism of the project.

The United States and some of its allies fear that Iran is using a civilian nuclear programme as a cover to enrich uranium for an atomic bomb. Tehran denies the allegations and says it is not seeking nuclear weapons.