National coach Gregor Townsend confirmed that the Edinburgh stand-off is now Scottish qualified and will be available for the game on the weekend of December 5-6 after quarantining on his return from his wedding in his native South Africa.
With Finn Russell and Adam Hastings both injured, Scotland have gone into the matches against Italy and France without their first and second choice fly-halves.
Weir has stepped in and impressed, particularly with his goalkicking, and while he is determined to hang on to the jersey, he is relishing more competition.
“Jaco has done really well for Edinburgh,” said Weir. “I know him well from my time there, so it will be great if he joins the squad and we can bounce off each other.
“I’m hugely passionate about playing for Scotland so every opportunity I get to represent my country and play at Murrayfield is a huge thing for me. I love every minute of wearing the national team jersey.
“I’m good friends with Adam and Finn – competition only spurs you on to play your best rugby – and those guys have been really supportive of me. I’m regularly in contact with Finn so it is great for me personally to have their backing.”
Scotland will not find out who they play until after the final round of group fixtures this weekend. The Scots’ final pool match, against Fiji, was cancelled due to a Covid-19 outbreak in the Islanders’ squad.