The Rock of the British overseas territory of Gibraltar, historically claimed by Spain, is seen at dawn near the border from the Spanish city of La Linea de la Concepcion, southern Spain, November 24, 2018. REUTERS/Jon Nazca

BRUSSELS (Reuters) - EU summit chair Donald Tusk said on Saturday that a Brexit summit on Sunday which had been in doubt over Spanish concerns on Gibraltar was now closer to going ahead as planned after he spoke to the Spanish prime minister.

“After the phone call between (European Council President Tusk) and (Spanish Prime Minister Pedro Sanchez) a few minutes ago, we are closer to tomorrow’s (European Council),” Tusk’s spokesman said on Twitter.

Sanchez had on Friday threatened to boycott the summit, which aims to sign off on the terms of Britain’s withdrawal from the EU in March, if negotiations that went on through Saturday failed to provide assurances that Madrid would have a strong say on how any post-Brexit treaty with London applied to Gibraltar.