MADRID (Reuters) -The Spanish government has unilaterally cancelled a contract to purchase ammunition rounds for its police force from an Israeli firm, a government source said on Thursday, ceding to pressure from its hard-left junior coalition partner Sumar.

Spain, a long-time critic of Israel's policies in the occupied Palestinian territories, pledged in October 2023 to stop selling weapons to Israel over its war with Hamas in Gaza and last year widened that commitment to include weapons purchases from Israel.

However, on April 17 as Spaniards geared up for the Easter holiday weekend, the government filed paperwork confirming the deal on the government tenders website.

The purchase, worth 6.6 million euros ($7.53 million), includes the acquisition of more than 15 million 9-mm rounds from Israel's IMI Systems, owned by Elbit Systems and represented in Spain by Guardian LTD Israel.

The decision drew a sharp rebuke on Wednesday from coalition partner Sumar, with one of the groups within Sumar, Izquierda Unida, threatening to withdraw from the minority coalition government.

The Interior Ministry responded that it had been advised by the state attorney that breaking the contract would mean paying the full amount without receiving the shipment.

On Thursday, a government source said it had decided to stick to its October 2023 commitment not to provide Israeli companies with arms or revenue flows "and nor will it do so in future".

The source said the Israeli company would be denied permission to import the defence material by the Spanish authorities on "public interest" grounds, the Interior Ministry would rescind the contract and government lawyers would respond to any subsequent legal claims.

Internal divisions over defence spending have already rattled the ruling coalition, threatening to deprive Prime Minister Pedro Sanchez of precious votes in parliament to pass legislation.

On Tuesday, Sanchez further angered Sumar, a platform of left-wing parties that controls five ministries led by deputy premier Yolanda Diaz, by announcing a wider plan to boost defence spending by 10.47 billion euros to meet NATO targets.

The minority government has struggled to pass legislation since securing a new term by cobbling together an alliance of left-wing and regional separatist parties in 2023.

($1 = 0.8767 euros)

(Reporting Inti Landauro, writing by Andrei Khalip, editing by Aislinn Laing, Bernadette Baum, William Maclean)