EU foreign policy chief Javier Solana has told President Pervez Musharraf that Pakistan's general elections next month must be "free and fair".
Mr Solana said that the level of the EU's future cooperation with Pakistan depended on these criteria.
He was speaking as Mr Musharraf began an eight-day visit to Europe, with democracy and tackling terror on the agenda as he meets EU leaders.
The EU is Pakistan's biggest trading partner, with annual trade worth $9bn.
Correspondents say that the EU chief did not give any clues as to what the EU's "future cooperation" with Pakistan may entail if it was satisfied over the fairness of the vote.
Not everyone is impressed by the president's 'charm offensive'
President Musharraf told a Brussels news conference that he raised issues such as Pakistani market access to the EU.
"I look forward to it in Pakistan because we need to sustain economic growth," he said.
Earlier President Musharraf said that he was determined the country would hold "free, fair, transparent and peaceful elections".
BBC Brussels correspondent Oana Lungescu says the Pakistani leader was bound to face tough questions about the conduct of a postponed general election now scheduled for next month, democratic reforms and the role of Pakistan in the fight against terrorism.
The president tried to reassure those worried about the course of democracy in his country and the delay in holding the vote, which was initially scheduled for January.
"We must have fair and transparent elections on 18 February," he said in Brussels.
"Whoever wins, obviously power will be handed over to them."
The president also tried to assuage the concerns of those worried about Pakistani human rights.
Critics say that the judiciary has been neutered
He said that Western preoccupation with the issue was "obsessive".
"You have taken centuries in reaching wherever you have come. Allow us time for going for the values that you have established for yourselves," he said.
The popular Pakistani independent television station, Geo TV, resumed broadcasting on Monday after the government lifted a ban imposed during emergency rule in November.
Correspondents say that the move could offset criticism that the president is gagging the media ahead of the elections.
"It is a wise and wonderful move, as elections are coming up (and) more media coverage would make the elections more credible and contribute to the positive development of the country," the station's President, Imran Aslam, told the AP news agency.
President Musharraf's visit will also take him to the UK, France and the World Economic Forum in Switzerland.
The tour is his first trip abroad since his controversial re-election and the murder of Pakistani opposition leader Benazir Bhutto.
The BBC's Barbara Plett in Islamabad says Mr Musharraf is deeply unpopular at home - members of civil society and opposition political parties do not accept his leadership, especially after his recent imposition of emergency rule.
Mr Musharraf told the European Parliament that instability in his country would not lead to the loss of control of its nuclear weapons.
He said that safeguards were securely in place.
"There is no chance at all of our nuclear assets falling into the wrong hands," he said.
He also rejected allegations that elements of the Pakistani military might be colluding with Islamist extremists.
His itinerary also includes meetings with his French counterpart, Nicolas Sarkozy, and British Prime Minister Gordon Brown.
He will also hold talks in Davos with US Secretary of State Condoleezza Rice, Afghan President Hamid Karzai and Iraqi Prime Minister Nouri Maliki.