ISLAMABAD, Pakistan  The widower of assassinated former Pakistani leader Benazir Bhutto took office as the country's new president Tuesday, facing immediate pressure to crack down on Islamic militants and address daunting economic problems.
Pakistan's top judge swore in Asif Ali Zardari at a brief ceremony in the presidential palace recently vacated by Pervez Musharraf, who resigned under pressure last month.
With his three children among the well-wishers and dignitaries packing a cavernous hall, Zardari, wearing a pinstriped business suit, beamed as the ceremony ended and shouts of "Bhutto is alive!" rang out.
But in the front row sat an imposing reminder of his task ahead: Afghan President Hamid Karzai, whose government accuses Pakistan of failing to take action against — even colluding with — Taliban militants based around the countries' common border.
The inauguration of Zardari, 53, completes Pakistan's return to civilian rule nearly nine years after then-army chief Musharraf seized power in a bloodless military coup.
The United States came to depend heavily on Musharraf for cooperation to capture or kill Al Qaeda leaders who plotted the 9/11 attacks on America and fled Afghanistan after the U.S.-led invasion in 2001 toppled their Taliban allies.
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However, the Taliban revived on Musharraf's watch, and Al Qaeda chiefs Usama bin Laden and Ayman al-Zawahri remain on the run, probably somewhere in the uncontrolled frontier region.
Zardari has made tough statements against Islamic extremism, and the army says it has killed hundreds of rebels in ongoing operations in several parts of Pakistan's volatile northwest.
The Pakistani Taliban have responded with a string of suicide bombings, including one in the city of Peshawar that killed 35 people Saturday, the same day as the presidential election by lawmakers.
Meanwhile, a rare assault by U.S. ground troops and a series of missile strikes into Pakistan's tribal region indicate that Washington is getting more aggressive about militant havens just beyond the Afghan border, despite intensifying Pakistani protests.
Officials said Tuesday the death toll from the latest missile strike had risen to 20 after residents and militants pulled more bodies from the rubble of a seminary and houses in a village in the North Waziristan region. Two Pakistani intelligence officials said the total included four suspected foreign militants.
In Washington, State Department spokesman Sean McCormack wouldn't say whether there had been a dramatic escalation of coalition operations on the border.
He said Washington looked forward to working with Zardari and his government on counterterrorism.
"They have a healthy appreciation for what's at stake here. And we have good cooperation with this government," McCormack said.
In the latest fighting, seven militants were killed Tuesday in northwestern Bajur region.
Additionally, six civilians, including three children, died when mortar shells hit two houses overnight in the same region, officials said. It was not clear who fired the mortar rounds.
Yet the elected government also has sought peace talks with militants, and many Pakistanis blame the rising violence in their own country on Musharraf's close alliance with Washington.
Musharraf quit reluctantly on Aug. 18 to avoid the threat of impeachment at the hands of a coalition of parties that routed his supporters in February parliamentary elections.
Musharraf made himself deeply unpopular by imposing emergency rule and purging the Supreme Court in November in order to halt legal challenges to his continued rule.
The ruling coalition, led by Zardari's Pakistan People's party, has collapsed over the failure to restore the judges.
But Zardari quickly found new allies, raising hopes that he can give Pakistan a degree of political stability, despite his lack of proven leadership skills and a reputation sullied by unproven corruption allegations.
Zardari won a two-thirds majority when lawmakers chose among the three presidential candidates on Saturday.
Ordinary Pakistanis are calling on the government to give them some relief from runaway inflation and massive power shortages. Economists are calling for urgent action to address slowing growth and investment plus fast-depleting foreign currency reserves.
Asif Ali Zardari has been sworn in as the President of Pakistan. The 53-year-old Zardari took oath from Chief Justice Abdul Hameed Dogar in Islamabad on Tuesday.

He took the oath as the twelfth President of Pakistan. On Sept. 6, Zardari, secured 479 votes from the total number of 702 votes of the electoral college consisting of two houses of the parliament and four provincial assemblies. 

Saeeduz Zaman Siddiqui, who was fielded by Pakistan Muslim League-Nawaz Group, received 153 votes while Senator Mushahid Hussain, a candidate from the Pakistan Muslim League-Quaid-e-Azam Group, got 43 votes.

Zardari is the widower of former Prime Minister Benazir Bhutto, who was assassinated Dec. 27, 2007. The election was called after former President Pervez Musharraf resigned last month.