European Union (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.

As negotiations among Spanish, British and EU officials wore into Saturday, Spanish Prime Minister Pedro Sanchez said he was ready to thwart his British counterpart May’s hopes of seeing EU leaders sign off on promises of close ties with London after Britain leaves the bloc in March if he did not get his way.