Washington: Ahead of the Nuclear Security Summit, the US has asked Pakistan to reduce its nuclear weapons arsenal as a responsible nuclear power. "It's important for Pakistan to really process that reality and put that front and centre in its policy," Secretary of State John Kerry said Monday, noting that the US and Russia were seeking to further reduce their nuclear warheads. Speaking at the inaugural session of the US-Pakistan Strategic Dialogue here, Pakistan Foreign Affairs Adviser Sartaj Aziz, however, sought greater US understanding of Pakistan's security concern and its desire to contribute actively to non-proliferation. "Our engagement on non-proliferation and strategic stability will continue, and Pakistan hopes to see greater US understanding of Pakistan's security concerns and its desire to contribute actively," Aziz said. As a mainstream nuclear power, Prime Minister Nawaz Sharif is looking forward to attending the Nuclear Security Summit in Washington on March 31, he said. Indian Prime Minister Narendra Modi is also expected to attend the summit. Earlier, welcoming Aziz, Kerry said: "Non-proliferation, nuclear safety is of obvious concern to both our countries, and I expect that we will continue to discuss the obligations of being a responsible state with nuclear weapons in the coming year." He noted that once both the US and the then Soviet Union had 50,000 warheads pointing at each other, but today, Russia and the US are operating under a treaty that has about 1,500 or so nuclear warheads. "And we are seeking to reduce that. So we're moving in the other direction," he said. "And I think it's important for Pakistan to really process that reality and put that front and centre in its policy."