Europe's ports face potential disruption next week as a deadline looms for international shipping to implement tough and expensive new ISPS rules to prevent a terror attack, a top German official said Thursday in Hamburg.

With the clock ticking toward the July 1 deadline, it was still unclear how strictly the new rules could be enforced without causing a "big hiccup" in trade and shipping, said Christoph Brockmann, head of shipping at the Federal Maritime and Hydrographic Agency of Germany, which is overseeing the implementation of the security measures.

"If everybody is going for strict measures in Europe, we will disrupt the European Community," Brockmann said, according to a Reuters report. By the start of this week, only 60 percent of the roughly 200 ships that call at German ports each day were in possession of an International Ship Security Certificate, which they will require by law from July 1, he said.

The U.N.'s International Maritime Organization says ships without valid certificates may be refused entry to ports, or they may be detained or expelled.

But Brockmann said "we will run into big trouble" if the rules are strictly applied and all such vessels are forced to anchor before entering port and submit to inspections. Within a couple of days, they would start to block access to terminals.

Authorities are also concerned that unless the rules are applied consistently, ship operators will transfer their business to ports that turn a blind eye. "There are a lot of harbors in Europe, and we are not quite sure what the other countries will do on July 1, so that makes things very, very difficult," Brockmann said.

"If there are different rules for treating ships . . . that automatically leads to uneven competition," said Harry Mohns, responsible for security at terminal operator Eurogate in the north German port of Hamburg.

Under the new IMO rules, port authorities, shipping companies and every individual vessel must have security officers and approved emergency plans.

Mohns said his company had to invest millions of dollars in items such as surveillance cameras, communications equipment and new electronic systems for checking the IDs of everyone entering its terminals. Its Hamburg facility was certified on Monday.