TRIPOLI, Libya – After giving a speech that emphasized the Islamization of Libya, the head of the transitional government on Monday tried to reassure the Western powers who helped topple Moammar Gadhafi that the country’s new leaders are moderate Muslims.

Just as in neighboring Tunisia and Egypt, Islamists have emerged from yet another Arab Spring uprising as the most powerful group in the country. But how far they will go will be decided at the ballot box — in Tunisia this week, in Egypt in November and in Libya within eight months.

National Transitional Council leader Mustafa Abdul-Jalil said Sunday that Islamic Sharia law would be the main source of legislation, that laws contradicting its tenets would be nullified and that polygamy would be legalized.

“I would like to assure the international community that we as Libyans are moderate Muslims,” said Abdul-Jalil, who added that he was dismayed by the focus abroad on his comments Sunday on polygamy. A State Department spokeswoman said the U.S. was encouraged that he had clarified his earlier statement.

The stir created by Abdul-Jalil’s address in Benghazi, the eastern Libyan city where the anti-Gadhafi uprising was born in mid-February, came as international pressure mounted on him to investigate the circumstances of Gadhafi’s death.

Abdul-Jalil ordered an inquiry to establish whether the deposed Libyan leader was killed in an execution-style slaying after being captured alive Thursday by fighters in his hometown of Sirte or whether he died in the crossfire as government officials have suggested.

State Department spokeswoman Victoria Nuland reiterated U.S. support for a full investigation but said “it’s now time for Libya to move on.” She endorsed the NTC’s proposed timeline for next steps in the democratic transition, and said Libyans “with no blood on their hands” must be ensured “a place in the new Libya, and that they are safe and they are included.”

She also called a Human Rights Watch report that dozens of Gadhafi supporters were found dead with bullet wounds in the back of the head and their hands tied, “extremely disturbing.”

Acknowledging the worldwide concern generated by calls for sharia law, Guma al-Gamaty, a London-based spokesman for the National Transitional Council, said Abdul-Jalil had an obligation to assure Libyans that Islam will be respected.

“This doesn’t mean that Libya will become a theocracy. There is no chance of that whatsoever. Libya will be a civic state, a democratic state and, in principle, its laws will not contradict democracy,” he said.

It is the kind of assurance Western powers that supported the anti-Gadhafi fighters with airstrikes and diplomatic backing may have been looking for.

In Washington, Nuland stressed the importance of creating “a democracy that meets international human rights standards, that provides a place for all Libyans and that serves to unify the country.”

She said the U.S. was encouraged that Abdul-Jalil clarified his earlier statements on the topic, but hedged on an overall U.S. assessment of systems based on Sharia.

“We’ve seen various Islamic- based democracies wrestle with the issue of establishing rule of law within an appropriate cultural context,” Nuland said. “But the No. 1 thing is that universal human rights, rights for women, rights for minorities, right to due process, right to transparency be fully respected.”