US Secretary of State Hillary Clinton on Wednesday congratulated Egypt's newly elected Islamist president, but cautioned that the election was just a first step towards true democracy.

"We have congratulated President (Mohamed) Morsi and the Egyptian people for continuing on their path to democratic transition," Clinton told reporters in Helsinki.

President-elect Morsi, of the once-banned Muslim Brotherhood, is in the process of forming a government after he was proclaimed Egypt's first democratically elected president on Sunday, a year and a half after street protests toppled veteran strongman and US ally Hosni Mubarak.

"We have heard some very positive statements so far," Clinton said, hailing among other things Morsi's pledge to honour international obligations, "which would, in our view, cover the peace treaty with Israel," signed in 1979 and which many feared could be abandoned with an Islamist in power.

However, Clinton cautioned, "one election does not a democracy make."

The historic vote was "just the beginning of hard work, and hard work requires pluralism, respecting the rights of minorities, an independent judiciary and independent media," she said.

"We expect President Morsi to demonstrate a commitment to inclusivity that is manifested by representatives of the women of Egypt, of the Coptic Christian community, of the secular, non-religious community and young people," she added.

Clinton also spoke Wednesday of Egypt's powerful military, which earlier this month assumed legislative powers after dissolving parliament following a court order and which maintains huge influence on policy-making.

The military "deserves praise for facilitating a free, fair and credible election," Clinton said.

US Defense Secretary Leon Panetta on Wednesday spoke to the head of the ruling military, Field Marshal Hussein Tantawi, and praised the generals for "their support for a secure, free and fair presidential election," a Pentagon spokesman said in Washington.

"Panetta and Tantawi emphasised the value of the enduring strategic relationship between the United States and Egypt, and noted Egypt's role as a pillar of regional peace and stability," press secretary George Little said in a statement.