Condoleeza Rice is being accompanied on the visit by her British counterpart Jack Straw, the UK's foreign minister.
A planned visit to a mosque in Straw's home town of Blackburn was canceled at the last minute after anti-war protesters planned to heckle her during prayer time, a mosque leader said.
Rice had planned to attend Friday prayers at Masjide Al Hidayah mosque, but anti-war protesters presented a security threat, said Ibrahim Master, a mosque official.
"It wasn't canceled because we don't like Condoleezza Rice," said Master.
A prominent poet and actress has also pulled out of planned appearances at a Liverpool Philharmonic concert Rice was to attend on Friday in protest at US policies.
But Rice said she wasn't surprised by the protests, calling it an essential element of a healthy democracy.
"People have the right to protest. That's what democracy is all about," she said in Blackburn, with Straw at her side.
Straw's Blackburn district has the country's third-highest Muslim population. Rice also is to meet Muslim leaders and the town's mayor, Ugandan immigrant Yusuf Jan-Virmani, on Saturday.
"People have the right to protest. That's what democracy is all about"
US Secretary of State
The protests were the reverse of the warm reception she received last fall when Straw accompanied her on a tour of her native Alabama.
Then, elderly white women lined up to shake the hand of a black native daughter made good, sports fans cheered and the tantalizing possibility of a run for president - something she discounts - surrounded Rice.
'Council of war'
"It's one thing to say this is a cultural visit, but others see it as a council of war," said Carmel Brown, an anti-war protester in Liverpool, describing the meeting between Rice and Straw.
During her visit the secretary of state is also expected to discuss the $256 billion Joint Strike Fighter jet deal between Britain and the US, as well as visit a British Aerospace factory to meet with some of the workers on the project.
Britain may be America's most trusted ally, but for months British concerns have been growing over how little the US trusts it with information about software codes and weapons systems that both countries have committed billions of dollars to make.
This month, Britain's top arms purchasing official told a US Senate committee more sensitive technology must be shared or Britain would not enter the next phase of the Joint Strike Fighter program and would cancel its plans buy 150 of the next-generation stealth aircraft.