Poland and the Czech Republic say they are in no hurry to conclude negotiations on a controversial US missile defence project.
The US plans a global shield to protect against "rogue" states
"It is not a race against time. The essential thing is to get what we want from the negotiations," said Polish Prime Minister Donald Tusk.
He has said Poland will only agree to provide a base for US interceptor missiles if it boosts Polish security.
He discussed the missile project with Czech leaders in Prague on Thursday.
He said both countries would co-ordinate their negotiations with Washington.
Czech Prime Minister Mirek Topolanek echoed his caution, saying "we prefer quality to speed".
The US wants to install interceptor missiles in Poland and a radar base in the Czech Republic, to protect against possible attack by what it calls rogue states, such as Iran and North Korea.
The Czech government aims to submit a draft accord on the radar base to parliament in April, Mr Topolanek said.
But he added that his government had not set any firm deadline for completing the negotiations.
Russia says the project will upset the military balance in Europe.
It has threatened to point missiles at Europe if the US stations parts of the new missile shield near its borders.
Deputy Foreign Minister Sergei Kislyak went to Poland on Thursday to discuss the defence shield.
Poland's new government is much more cautious than its predecessor on the issue, a BBC correspondent says.
"Our agreement to a missile defence installation in Poland is going to be directly tied to... increasing Poland's security," Mr Tusk said on Wednesday, quoted by the Associated Press.
Poland now wants US military hardware and a bilateral security agreement before it agrees to host the base, the BBC's Adam Easton reports from Warsaw.
It is also wary of striking a deal ahead of the US presidential elections later this year.
Mr Tusk is concerned a new administration in Washington may abandon the missile defence plans.
Polish Defence Minister Bogdan Klich is to discuss the issue with his US counterpart Robert Gates in Washington later this month.
The BBC's Rob Cameron in Prague says there is heavy opposition to the plans in the Czech parliament and a recent survey of public opinion there found 70% of people opposed to the defence shield.