European Union governments are due to make a ruling on whether or not to blacklist the military wing of Hezbollah after allegations that the Lebanese group has stepped up its activities in Europe.
Britain has sought to persuade its EU peers since May to put the Shia Muslim group's armed wing on the bloc's terrorism list, citing evidence that it was behind a deadly bus bombing in Bulgaria last year.
EU foreign ministers will discuss the issue on Monday in Brussels. Putting an organisation on the terrorist blacklist needs unanimity among the 28 member nations.
Until now, the EU has resisted pressure from Washington and Israel to blacklist Hezbollah, arguing that it could fuel instability in Lebanon, where the group is part of the government, and add to tensions in the Middle East.
Diplomats say the opposition to such a move is fading.
"There are still reservations, but we are moving towards what could be a decision on the possible listing," a senior EU official told the Reuters news agency.
"The number of member states which have difficulties with a possible decision has been slowly diminishing."
Blacklisting the military wing would mean the freezing of any assets it may hold in the 28-nation bloc, though officials say there is scant information on the extent of Hezbollah's presence in Europe or on its assets.
Britain, backed by France and the Netherlands among others, has argued that Hezbollah's growing involvement in the Syrian war means Lebanon is already in a fragile situation and that the EU must weigh the possibility of future attacks in Europe.
Political wing unaffected
While it is unclear what exact form any restrictions would take, EU governments are expected to make it clear that they will continue to speak to any political groups in Lebanon, including Hezbollah.
On Thursday, Lebanon asked Brussels not to blacklist Hezbollah on the grounds the group was an "essential component of Lebanese society".
Certain EU member states echoed concern that the move would break off EU diplomatic contact with the group.
"A few member states wanted to be reassured that such a decision will not in any way jeopardise political dialogue," the senior EU official told Reuters.
Some EU diplomats, responding to concerns that sanctions could further radicalise the group, have argued that targeting the military wing could, in the long term, persuade some of its members to move away from violence into the political sphere.
Hezbollah denies any involvement in last July's attack in the Bulgarian coastal resort of Bourgas that killed five Israelis and their driver.
But the Bulgarian interior minister said last week that Sofia had no doubt the group was behind it.
In support of its bid to impose sanctions, Britain has also cited a four-year jail sentence handed down by a Cypriot court in March to a Hezbollah member accused of plotting to attack Israeli interests on the island.