Semedo, 23, was the focus of a €30m bid from Barcelona this week, but the Primeira Liga champions are said to be refusing to lower their €50m valuation.
In an effort to speed up the signing, Barcelona's sporting director Robert Fernandez has travelled to Lisbon to force the move through as pre-season gets under way across Europe.
Fernandez has travelled with Javier Bordas, another member of the Camp Nou board, in view of agreeing a price for Semedo and closing a deal as quickly as possible.
Barcelona have failed to fill the void which was left by Dani Alves' exit last summer, with Sergi Roberto and Aleix Vidal failing to impress in Catalunya.
BARCELONA END BELLERIN CHASE
Semedo emerged as Barcelona coach Ernesto Valverde's first-choice right back after the Liga giants were told Arsenal's Bellerin was not available at any price.
A product of La Masia, Bellerin left Barcelona in favour of Arsenal in 2011 but has long been linked with a return to his boyhood club.
The Spain international, 22, was seen as the long-term answer to the club's right-back problem by former manager Luis Enrique, though a deal never transpired.
Bellerin made 27 Premier League starts last season and impressed Barca scouts throughout the campaign, becoming one of the club's priority targets in the summer window.
But he's no longer a target following a stand-off with the north London side over his future and he's expected to remain at the Emirates Stadium.