U.S. Defense Secretary Donald Rumsfeld says Afghanistan's government should take the lead to curb the country's opium production.

Speaking to reporters Wednesday in the capital, Kabul, Secretary Rumsfeld voiced concern over Afghanistan's drug cultivation problem.

"It leads to other types of crime and corruption," said Mr. Rumsfeld. "It is a very dangerous thing, and needless to say, the principle responsibility falls to the government."

He said United States and other countries stand ready to take the Afghan government's lead in tackling the problem.

The remarks follow Mr. Rumsfeld's earlier statements that opium crops in Afghanistan may be used to fund anti-government militancy in the country.

Both the U.S. and Afghan governments have promised increased operations in the near future to fight the Afghan drug trade, said to account for three quarters of the world's opium poppy cultivation.

Mr. Rumsfeld also repeated his praise for Afghanistan's democratic development, including the country's first post-war presidential and parliamentary elections, slated respectively for October and April.

He said that voter registration efforts had exceeded expectations, which he said had only several months ago predicted up to five million registered voters.

"I visited the Joint Election Commission today and they claimed something in excess of nine million registered voters, of which a very sizable portion are women," he said.

Afghan transitional President Hamid Karzai joined Secretary Rumsfeld at the news conference, saying the registration drive had succeeded in spite of efforts by insurgents to disrupt it.

He said Mr. Rumsfeld's many recent visits to Afghanistan were themselves proof of Afghanistan's improvements after over two decades of war.

"Fortunately for us as a friend, he's become a frequent visitor to us, which is a good sign, which means that Afghanistan is making progress," said Mr. Karzai.

While U.S. officials have not endorsed any of the 18 Afghan presidential candidates now officially registered for the election, Afghan and international media often describe Mr. Karzai as the closest to the United States.