TEL AVIV — Israel’s defense minister and Labor Party chairman, Ehud Barak, threatened to help the opposition dissolve parliament if the ruling Kadima Party doesn’t move to replace Prime Minister Olmert.

Mr. Barak gave Kadima two weeks to act, stepping up his campaign against Mr. Olmert after a meeting yesterday with members of the Labor Party, which holds 19 seats in the 120-seat Knesset. As the second-biggest bloc in Mr. Olmert’s coalition, Labor’s departure would bring down his two-year-old government.

“First, we will listen to the decisions of Kadima,” Mr. Barak, a former prime minister, said in remarks broadcast on Israel Radio from the party’s headquarters in Tel Aviv. “If the situation requires it, we will bring about a first reading of the bill to dissolve the Knesset.”

Mr. Olmert, 62, has been under pressure to step aside amid a police investigation into allegations he accepted more than $150,000 from an American businessman, Morris Talansky, before he became prime minister. Foreign Minister Tzipi Livni, who said Kadima should plan for new elections, is the leading candidate to replace Mr. Olmert. He denies he’s done anything wrong.

Mr. Olmert, who must call an election by 2010, gave his approval yesterday to start preparations for advancing Kadima’s primary. By stepping down, he could temporarily hand power to Mr. Livni without the need for early elections.

Setting up a plan for a primary election may take longer than two weeks because Kadima is a new party that was just set up in 2005, an Olmert spokesman, Mark Regev, said.

Also yesterday, at least seven Palestinian Arabs were killed in Gaza Strip violence, four of them in an explosion at a house and three others as they raided an Israeli border post. Two people were injured by Palestinian rockets.

The blast at a home in the northern Gaza town of Beit Lahiya was probably caused by explosives inside the house, the chief of emergencies at the Palestinian Health Ministry, Mo’aweya Hassanein, said by phone. About 25 people were injured.