Security forces increased patrols on some streets in the Afghan capital and blocked others entirely Wednesday, bracing for possible militant attacks during the inauguration ceremony that will cement President Hamid Karzai's tumultuous re-election victory.

Karzai will be sworn in Thursday for his second five-year term, with many in the international community hoping he will introduce solid reforms and pave the way for a Cabinet house-cleaning to rid the administration of corrupt officials.

The inauguration comes amid repeated calls and threats from the international community that he reform his government following an election so spoiled by fraud that it took two and half months to resolve.

U.S. Secretary of State Hillary Rodham Clinton — who arrived in Kabul on Wednesday to attend the ceremony — said Karzai's inauguration provides a new chance for him to strengthen government accountability.

"There is now a clear window of opportunity for President Karzai and his government to make a new compact with the people of Afghanistan to demonstrate clearly that they're going to have accountability and tangible results that will improve the lives of the people who live throughout this magnificent country," Clinton told employees at the heavily secured U.S. Embassy compound in Kabul.

Clinton's trip comes days after U.S. Ambassador to Afghanistan Karl Eikenberry, in leaked memos, questioned the wisdom of adding American troops at a time when the Afghan political situation is so uncertain.

Both the U.S. and other NATO countries have said they are weighing the rampant government corruption and mismanagement in decisions on committing more troops.

Clinton also met with the top U.S. military commander in Afghanistan, Gen. Stanley McChrystal, who has advocated sending tens of thousands of additional U.S. troops.

"Nobody knows better than our military commanders that troops alone cannot meet our goals of defeating al-Qaida, of helping the Afghans get the capacity to defend themselves and provide governance that will result in positive changes for the people of this country," she said.

Clinton has said the U.S. will not provide civilian aid to Afghanistan unless it can be sure the government can be accountable for the funds. For his part, Karzai complains that millions of dollars in foreign aid is being wasted before it ever gets to the Afghan people.

Even the ceremony itself is fraught with potential danger. Representatives from 42 countries are to attend, and the event could be a target for militants.

The inauguration will be held inside the presidential palace with tight restrictions on who is allowed in. Since an assassination attempt on Karzai at a public parade in 2008, he has stayed away from large public appearances.

The government has declared Thursday a national holiday and has asked people to stay home to minimize traffic on the capital's clogged roads, while regular flights to and from Kabul airport will be canceled for the day. A number of neighborhoods in Kabul have been closed completely to traffic, with exceptions made for ambulances. Helicopters circled the city Wednesday.

Col. Sanam Gul, commander of the 4th Battalion of the Afghan National Army, the key Afghan combat unit in Logar province south of the capital, said his troops along with U.S. forces were increasing patrols and checkpoints leading into Kabul and stopping suspicious vehicles headed in that direction.

"The enemy is now trying to penetrate into Kabul to disrupt the inauguration," Gul said.

Afghan Defense Ministry spokesman Mohammad Zahir Azimi said patrols have been stepped up throughout the capital, and that roads leading to embassies have been blocked.

"We have very tight security inside Kabul, around Kabul, outside Kabul," he said.

The inauguration comes as the reputation of the Karzai government has sunk to new lows. Though dogged by corruption for years, the government was seen as particularly tainted by the August presidential vote and the rampant ballot-box stuffing that took place.

Afghan flags hung from lampposts on major boulevards to welcome the dozens of international leaders in town for the inauguration, including Pakistani President Asif Ali Zardari, who met with Karzai on Wednesday.

Traditionally rocky relations between Pakistan and Afghanistan have improved since Pakistan's elected government led by Zardari replaced the military dictatorship of Gen. Pervez Musharraf.

Meanwhile, in the latest violence, a U.S. service member was killed when his vehicle hit a bomb in southern Afghanistan, NATO forces said.