President Bush and British Prime Minister Tony Blair (searchoffered their condolences Thursday and vowed to continue their fight against global terrorism just hours after another terrorist attack in Istanbul -- this one on Western targets -- killed 27.

"We are united in our determination to fight and defeat this evil wherever it is found," Bush said during a joint news conference at the Foreign and Commonwealth Offices (searchin London.

The Turkish attacks on the British consulate and the London-based HSBC bank in downtown Istanbul shows the "wretched and backward philosophy of the terrorists," Blair said.

"This is a time to show strength and determination and complete resolve. This terrorism is the 21st century threat. It is a war that strikes at the heart of all we hold dear," Blair said.

The attacks were sure to refocus attention on the continuing danger of terrorism at a time when both Bush and Blair are warning against complacency.

On Wednesday, Bush ticked off a list of recent terrorism targets around the world -- including another terror attack in Istanbul just days ago.

On the second full day of his 3 1/2-day visit to Britain, Bush and his wife, Laura, also had an emotional meeting with family members of seven British soldiers killed in Iraq. They met in the Dean's Chapel of Westminster Abbey (search).

Earlier, the president laid a cream-colored wreath with a red, white and blue banner at the Tomb of the Unknown Warrior (searchin a subdued ceremony at the cathedral.

Heading into their meeting at No. 10 Downing Street (search), Bush and Blair were seeking to project unity at a time when Blair's approval ratings have sunk amid broad opposition to the war.

While Bush celebrates the two countries' friendship as "one of the great alliances of mankind," many of the British deplore the war, and as many as 100,000 protesters were expected to show their discontent Thursday in a massive march.

Gillian Siddons, a cook from Auchenblae in Scotland, stood near Westminster Abbey Thursday wearing a sign saying "Who wants democracy Bush-style?"

About 100 protesters also gathered opposite Blair's Downing Street office, some wearing orange jumpsuits and masks to protest the United States' holding, without trial, nine British terror suspects at Guantanamo Bay, Cuba.

Some protesters said they were uncomfortable with Blair's close relationship with the U.S. president.

"We're angry that Bush appears to be leading our country," said Ted Edwards, a gas supply worker who took the day off to attend the march. "Why Blair is allying himself to Bush I do not know. It's important to show our anger at Bush and to tell Blair he doesn't represent most people in Britain."

Bush said he was not dismayed by the demonstrations that have accompanied his visit.

"Freedom is beautiful," the president said, adding he was happy to be in a country where people were allowed to speak their minds freely. "All I know is that people in Baghdad weren't allowed to do this until recent history."

Bush also is trying to showcase a softer side of U.S. foreign policy by convening a round-table gathering on American efforts to combat AIDS in Africa and the Caribbean.

Blair faced tough questions about the war Wednesday at the House of Commons, but did not back down from his support of the United States.

"It really is about time we started to realize who our allies are, who our enemies are, stick with the one and fight the other," Blair added, to loud cheers from lawmakers. An unidentified protester was ejected from the public gallery in the Commons after shouting "he's a war criminal, he's a war criminal" just as Blair was discussing Bush's visit.

During his visit, Bush hopes to turn the tide of public opinion here and across Europe. Bush said the greatest danger facing Western democracies is weapons of mass destruction in the hands of terrorists and dictators like Saddam Hussein.

"If they gain the weapons they seek, they will kill by the millions and not be finished," Bush said. "The evil is in plain sight. The danger only increases with denial.

"Great responsibilities fall once again to the great democracies," he said. "We will face these threats with open eyes and we will defeat them."

Bush tried to erase European doubts about the Iraq war by comparing the threat posed by Saddam to Nazi aggression, communism and ethnic cleansing that once menaced the continent.

"Let us never forget how Europe's unity was achieved: by allied armies of liberation and NATO's armies of defense," Bush said.

While he was shielded from most of the demonstrators in London on Wednesday, Bush seemed fully aware of his detractors.

Bush joked that the last prominent American to visit London was David Blaine, the magician who lived in a clear box over the Thames River for 44 days. "A few might have been happy to provide similar arrangements for me. I thank her majesty the queen for interceding," Bush said.

Also on Wednesday, Liberal Democrat leader Charles Kennedy said Bush told him during a meeting Wednesday that he hoped the Guantanamo Bay controversy could be resolved "in the next week or two."

Opposition Conservative Party leader Michael Howard said on Thursday, however, that a meeting with Bush left him uncertain whether an agreement was near.

Blair was expected to press Bush on the matter during their meeting, but White House officials said they did not expect a resolution during Bush's trip here.

The Associated Press contributed to this report.