Europeans have given a cool reception to Bush's plan to bring together the world's biggest polluting countries by year-end to explore ways of limiting emissions and agree on a long-term goal by the end of 2008.
Some portrayed it as a defeat for Angela Merkel, the German chancellor and host of the G8 summit, who wants the group to agree now on a need for cutting emissions of greenhouse gases about 50 per cent by 2050.
In Prague, Bush will talk about the need to advance democracy at an international conference organised by human rights and pro-democracy activists, including Vaclav Havel, the former Czech president.
Havel was a leader in the "Velvet Revolution" that ended communism in the former Czechoslovakia.
"The president also appreciates the Czech Republic's leadership in promoting freedom in some of the world's most tyrannical societies, such as Burma, Belarus and Cuba," Stephen Hadley, the White House national security adviser, said.
Bush will thank Poland for co-operating in the missile defence system, promoting freedom in Belarus and helping young democracies such as Ukraine, Hadley said.
One of the most watched meetings during the summit will be with Vladimir Putin, the Russian president, whose escalating criticism of the USs has raised concerns about the deterioration of US-Russian ties.
Putin vehemently opposes US plans for a missile defence shield in the Czech Republic and Poland, seeing it as a threat to Russia.
Bush has asked Russia to join in the defence system, saying it is intended as protection from potential threats from other states such as Iran.
Putin warned in an interview released on Sunday that Russia would revert to its Cold War stance of aiming missiles at Europe if Washington pursued its plan.
He acknowledged that such a response risked reviving an arms race in Europe but said Moscow could not be blamed because Washington had started the escalation.
Opponents contend that the shield - which the US says would help protect both it and Europe from a rocket attack by Iran - could make Czechs a target for terrorists and re-ignite Cold War-era tensions between Washington and Moscow.
Hundreds of demonstrators had planned to rally on Monday evening on a square near the medieval Prague Castle before Bush's arrival.
A smaller rally by communist youth also was planned outside the US embassy.
Polls say that more than 60 per cent of Czechs oppose the idea of hosting the radar system, which would be built inside the Brdy military zone southwest of Prague, and surveys in Poland suggest just one in four Poles wants the missiles.
Bush's visit to Albania, the first by a sitting US president, comes as the US locks horns with Russia over the issue of statehood for Kosovo, which is majority ethnic Albanian.
The US supports a plan proposed by Martti Ahtisaari, the UN mediator, which offers Kosovo independence under international supervision.
Russia opposes the plan.
The last stop in Bulgaria will highlight promoting democracy in the Balkans.