BAGHDAD - On the last day of the official U.S. combat mission in Iraq, there was no dancing in the streets, no celebratory gunfire and no sense that a milestone had been reached.

U.S. troop levels have dropped to just below 50,000, fulfilling an Obama administration pledge to move from combat to stability operations. But as the United States prepares to declare the end of its seven-year-long war, Iraqis are bracing for uncertainty.

On Tuesday, Interior Minister Jawad Bolani said that the country is on high alert and that Prime Minister Nouri al-Maliki has created two security crisis cells - one for Baghdad and one for the rest of Iraq. The cells would respond in case violence escalates in coming days.

Bloodshed has already increased as Iraq nears the end of its sixth month without a government since national parliamentary elections. Many Iraqis also say they worry that another country could fill the vacuum left behind by the United States and that the security gains of the past two years could erode.

"Right now we are in a state of emergency. Our brothers in the Ministry of Defense are sleeping in the ministry until this stage is finished," Bolani told reporters Tuesday.

Maliki met Tuesday morning with Vice President Biden, who is making his sixth visit to Baghdad on behalf of the Obama administration. At the start of the meeting, Biden questioned media reports of an increase in violence.

"It's much safer," Biden said. Reporters following the vice president Monday were asked to wear body armor and helmets, and Biden was heavily guarded throughout his trip.

Outside the heavily fortified Green Zone, where many of Biden's meetings took place, Iraqis expressed fear and frustration.

"We wanted change, and nothing's changed," Mohammed Imad, 21, said, leaning against a wall covered in old election posters.

Despite the fears voiced in the streets, Maliki declared Tuesday a day of "celebration."

"This is a day that will remain in the memory of all Iraqis. Today, Iraq has become a sovereign and independent country," the prime minister said on state television. "Unfortunately, we are facing a campaign of doubt."

"Whose celebration is this?" asked Ibrahim Abdul Wahab, 57, a resident of Haifa Street in downtown Baghdad, where Sunni insurgents were in control more than two years ago. "It's his, not Iraq's. Where are the promises of the planned democracy?"