By Louisa Lim
BBC News, Beijing
North Korea's premier has arrived in China, a day after the US hinted at sanctions if Pyongyang did not return to talks on nuclear disarmament.
Economic issues will be high on Pak Pong-ju's agenda
Pak Pong-ju's trip comes just hours after his country announced that it had increased its nuclear arsenal to counter any enemy invasion.
However, the main focus of the six-day visit seems to be economic.
Mr Pak is scheduled to tour a mobile phone plant in the capital, Beijing, before visiting Shanghai.
Mr Pak is a technocrat charged with reviving North Korea's dismal economy.
Ms Rice urged China to use its influence over Pyongyang
He arrived in Beijing at a time when Pyongyang is under the international spotlight.
US Secretary of State Condoleezza Rice on Sunday urged North Korea to return to six-party talks on its nuclear ambitions.
If it did not, she warned, "other options" would be considered.
As North Korea's biggest supplier of food and fuel, China's leverage is judged crucial to the future of talks.
But Beijing fears taking any action which could lead to the collapse of its impoverished neighbour.
Earlier on Tuesday, North Korea's radio announced the country's nuclear arsenal was being boosted.
Analysts say it was a signal that the Stalinist state is unwilling to respond to international pressure.