BBC: Bulgaria Presses Bush on Shield
Bulgaria's government, a staunch US ally, is concerned it may be left out of the plan, which would include bases in Poland and the Czech Republic.
The issue has contributed to raised tensions between the US and Russia.
Mr Bush also backed Bulgarian calls to free five nurses sentenced to death in Libya on charges of infecting children with HIV.
Speaking at a news conference with his Bulgarian counterpart Georgy Parvanov in Sofia, Mr Bush said the nurses' release was a "high priority".
Mr Bush spoke as an EU delegation was in Libya attempting to negotiate the release of the five.
"They should be released and they should be allowed to return to their families," he said, adding that the US would make representations to Libya on behalf of the Bulgarian authorities.
Mr Bush's trip to Sofia is the final leg of an eight-day European tour including visits to the G8 summit in Germany, the Czech Republic, Poland, Italy and Albania.
During formal talks with President Parvanov and Bulgarian Prime Minister Sergey Stanishev, Mr Bush thanked Bulgaria for its support in Iraq and Afghanistan.
Thirteen Bulgarians have been killed in Iraq, while the country's 200-strong force in Afghanistan is soon to expand to 800 troops.
More than 3,000 US troops are due to start arriving at a new base in Bulgaria in September, as part of a US policy to move many of its European forces closer to the Middle East.
The former Communist bloc nation joined Nato in 2004, and became a member of the European Union this year.
But Bulgaria remains concerned that despite its loyalty, much of the country would fall outside the range of the US missile shield.
However, talks to include Bulgaria in the missile defence plans will only inflame tensions with nearby Russia, which views the system as a threat and a challenge to its influence in the region, says the BBC's Jonathan Beale.
Russia opposes the plan, which it regards as a threat, and President Vladimir Putin has threatened to point Russian missiles at Europe in response.
The US says its missile shield is not directed at Russia, but at what it considers "rogue states" such as Iran.
On Sunday, Mr Bush received a hero's welcome in Albania, another staunch ally, and reiterated his support for a UN plan for independence for Kosovo.
His sentiments were welcomed in Kosovo but rejected by a spokesman for the Serbian government, which opposes independence.
The G8 failed to reach a consensus on the Kosovo issue at a summit last week.
Russia remains strongly opposed to the blueprint for independence laid out in April by UN special envoy Martti.
The Albenians "LOVE" Bush because they hope he will give them Kosovo.
This is the human psychic...people LOVE when you give them and HATE when you take something away from them!
what they do not realize...Bush is week already...he does not have much to say in
a congrees,dominated by democrats.
Anyway...you are wrong,Vlas...the Bulgarian Romas came to Bulgaria from Egypt.
They may stem from Northern India and sometime in the middle-ages they moved
West-northwards,looking for better pastures for their annimals.
The American Indians did NOT come from India ...there are different theories...some triobes came to North America over the Baring Strait to Alaska;some came from the Polyneasean Islands.
What has he done for the Albanians to make him such a 'zero hero'? What does the United States have in store for the Balkans? And how else are the dreaded Albanians involved? Other then doing the dirty work for the United States like NATO does, will the United States provoke more terror and strife by unleashing the Kosovo Liberation Army loose again, this time on the unsuspecting populaces of Bulgaria and Romania? This is the 'Grand American Illusion' at work...make promises, tell lies, use double-talk to pacify and deceive, and to hell with the rest! Just ask what is left of the native American Indian tribes to remind the Balkans just how benevolent and humanitarian the 'Grand American Illusion' was for them...that is why many American Indians were transported to Bulgaria by the American government...to find a better way of life on the Bulgarian plains and valleys. They are called Roma nowadays.