Israel on Friday took the offensive in its battle to prevent hundreds of pro-Palestinian activists from arriving at its main airport by discouraging airlines from flying them, an official said. \"Israel has given airlines a list of 342 unwanted people, warning them that they will be immediately turned back at the expense of the companies,\" Israeli immigration spokeswoman Sabine Hadad told AFP. Following the warning, \"the companies have already refused to take on board around 200 of these passengers,\" she said, adding that two US activists who arrived overnight were sent back to the United States. The two American women had originally been involved in a scuppered bid by activists to sail to the Gaza Strip on a 10-boat flotilla in defiance of an Israeli naval blockade of the Palestinian coastal territory. Some 50 airline passengers who described themselves as \"pro-Palestinian\" were prevented from embarking on a flight to Israel from Geneva airport on Friday, officials said, prompting flight delays. \"This morning passengers for an easyJet flight were prevented from embarking,\" airport spokeswoman Aline Yazgin told AFP, adding she did not know why they had been prevented from boarding. She said that as a result several people belonging to a French group of pro-Palestinians had tried to get past airport security doors, resulting in authorities temporarily shutting down boarding areas. At Roissy airport in France, at least nine activists were prevented from boarding a flight of Hungarian carrier Malev to Tel Aviv via Budapest. \"Their reservation was cancelled at the request of Israeli authorities who have drawn up a list of undesirable persons,\" an airport source said. Organisers of the \"Welcome to Palestine\" campaign, which some have called the \"flytilla,\" had said up to 800 activists were to fly in to Ben Gurion airport on Friday in a peaceful mission to visit Palestinian families. In a statement on Friday they condemned the Israeli pressure on airlines and threatened legal action. \"We call on all airline companies not to accept such provocative, blackmailing, and illegal actions by the Israeli government,\" it said. \"Visitors travelling between countries have rights under international law and bilateral travel agreements,\" it added.\"Those who had reservations cancelled will exercise their right of protest including bringing legal cases in their own countries.\" The organisers were planning to hold a press conference on Friday in the West Bank town of Bethlehem. Hundreds of police are on standby at the airport near Tel Aviv, but no incidents have been reported so far on Friday. Israel\'s tourism ministry said it would mount a charm offensive over the weekend at the airport, where thousands of tourists were expected to arrive. \"Tourists will be greeted by the ministry’s staff who will hand out flowers and tourism information and who will provide general assistance according to individual needs,\" it said in a statement, adding that Tourism Minister Stas Miseznikov would visit the airport on Friday. \"The ministry of tourism will make sure to receive tourists respectfully, sending the message that Israel is a safe country and an attractive tourism destination,\" it said. \"Dealings with pro-Palestinian activists and the responsibility of the various security forces, should not affect the airport’s activities.\"