US Vice President Dick Cheney is in Afghanistan to bolster the country's fragile government as it struggles with rising threats from al-Qaida and Taliban militants. Cheney flew to the Afghan capital from Oman early Thursday and went immediately to the presidential palace to meet with President Hamid Karzai. Reporters were not allowed to report on Cheney's visit until he had arrived safely. Cheney spokeswoman Lea Ann McBride says US President George W. Bush asked Cheney to meet with Karzai in advance of a NATO summit next month in Romania. This is Cheney's fourth vice presidential trip to Afghanistan. He was in Iraq earlier this week as part of a 10-day trip to the Middle East.