United States Democratic presidential hopeful Barack Obama is due to hold talks with President Hamid Karzai in Kabul today, the Afghan government said, on the second day of a visit to the insurgency-hit country.

It was not clear what time Obama would meet Karzai since details of trips to Afghanistan by prominent personalities are often kept secret for security purposes.

Obama and other US senators arrived in Afghanistan yesterday and met US military commanders at the main American base at Bagram, north of Kabul, for a briefing on the international effort against the Taliban and other extremists.

The delegation later flew to a base in eastern Afghanistan, closer to the border with Pakistan, where they met some of the 36,000 US soldiers in Afghanistan, the US-led coalition said in a statement.

The presumptive Democratic presidential nominee has been critical of Karzai's government, saying in an interview with CNN this month that it had not "gotten out of the bunker" to rebuild the war-torn country.

Obama's comments drew immediate fire from Republicans, who accused him of insulting a key US "war on terror" ally and ignoring multiple assassination attempts against Karzai.

"I think the Karzai government has not gotten out of the bunker and helped to organise Afghanistan and (the)government, the judiciary, police forces, in ways that would give people confidence," Obama said. "So there are a lot of problems there."

The Illinois senator has also accused the Bush administration of allowing Al-Qaeda and the Taliban to regroup by diverting vital US forces to the war in Iraq.