(Adds comment from May's office)
By Costas Pitas
LONDON, June 4 (Reuters) - British business leaders warned Prime Minister Theresa May during a meeting on Monday that maintaining frictionless trade with the European Union after Brexit was probably more important than the imposition of any tariffs, a source told Reuters.
May and several top ministers met business chiefs including the bosses of pharmaceuticals giant GlaxoSmithKline, supermarket Tesco, carmaker Aston Martin, telecoms firm BT and construction company Balfour Beatty to discuss Brexit.
"A frictionless border is probably even more important than the levy or tariff," a source familiar with the contents of the meeting told Reuters when asked about what May had been told.
"Several people around the table said that," the source said on condition of anonymity due to the confidential nature of the discussions.
May has ruled out Britain staying in a customs union with the EU bloc - to the dismay of many business leaders - and says her government is working on two possible solutions to minimize delays at Britain’s ports and airports.
The customs conundrum - which will define commerce between Britain and its biggest trading partner for decades - is a test of May’s leadership as she tries to pacify rival factions in her Conservative Party and her cabinet.
Business leaders were told a decision from ministers was "imminent", the source said.
After the meeting, May's office said that she and Brexit minister David Davis had provided an update on talks with the EU and told attendees they planned to set out Britain's future relationship with the bloc in a white paper policy document soon.
"The business representatives expressed their support for this approach, which will build on information provided through the prime minister's various speeches," Downing Street said in a statement.
International trade minister Liam Fox also discussed foreign investment into Britain with business leaders. One attendee said that Britain needed to become predictable again, as it had been in the past, to help secure further spending, according to the source. (Reporting By Costas Pitas. Editing by Andrew MacAskill)