Germany captain Bastian Schweinsteiger and forward Lukas Podolski have been included in the 27-man provisional squad for Euro 2016, along with youngsters Leroy Sane and Joshua Kimmich.
Schweinsteiger, 31, partially tore the medial collateral ligament in his right knee while with the national team in late March but said at the start of the month that he was "very confident" he would be fit for the tournament.
"Bastian is our captain," Germany head coach Joachim Low told reporters at a news conference in Berlin. "He's doing full running training.
"We will have to see about his state of fitness when he joins us next week, and whether he can train with the team. We'll have to make a decision by the end of May."
Schalke winger Leroy Sane, 20, won his first cap for Germany in November but returned to Germany's under-21 side in March, although Low said at the time he remained in contention for Euro 2016.
He will now get the chance to prove he is worthy of a place in the final 23-man squad at the training camp, and Low said: "Leroy Sane has extraordinary abilities. He has that something special."
Borussia Dortmund's Julian Weigl and Bayern Munich's Joshua Kimmich have also been included despite not yet having made a senior appearance for Germany, along with Bayer Leverkusen midfielder Julian Brandt.
Brandt, 20, was key to Leverkusen's revival in recent weeks as he scored in six consecutive matches from late March through to early May.
"Weigl plays a really good role at Dortmund," Low said. "Kimmich is versatile -- he's played at a high level at Bayern. Julian Brandt is a young player and he's on a roll right now. He's played well in the past few weeks."
Alle Spieler auf einen Blick: Das ist unser vorläufiger Kader für die #EURO2016! #DieMannschaft #JederFuerJeden pic.twitter.com/WGaLEdakOn
- Die Mannschaft (@DFB_Team) May 17, 2016
Low also defended the selection of former Arsenal forward Lukas Podolski, who currently is playing for Galatasaray.
"Lukas Podolski still has a sporting value for the national team, even though a few don't believe it," he said. "He's also an important personality for the team."
The 30-year-old will only join the Germany team following the Turkish cup final against Fenerbahce on May 26.
The final 23-man squad must be submitted by May 31.
Germany are to play one official friendly match before submitting the final squad, against Slovakia on May 29, although there will also be a meeting with the under-20 side in the training camp.
They then take on Hungary on June 4 in their last preparation game before facing Ukraine in their first group match of the European Championship on June 12.
Provisional 27-man Germany squad for Euro 2016
Goalkeepers: Manuel Neuer (Bayern Munich), Bernd Leno (Bayer Leverkusen), Marc-Andre ter Stegen (Barcelona)
Defenders: Jerome Boateng (Bayern Munich), Mats Hummels (Borussia Dortmund), Emre Can (Liverpool), Jonas Hector (Cologne), Benedikt Howedes (Schalke), Shkodran Mustafi (Valencia), Sebastian Rudy (Hoffenheim), Antonio Rudiger (Roma)
Midfielders: Mario Gotze (Bayern Munich), Mesut Ozil (Arsenal), Sami Khedira (Juventus), Toni Kroos (Real Madrid), Karim Bellarabi (Bayer Leverkusen), Julian Brandt (Bayer Leverkusen), Julian Draxler (Wolfsburg), Joshua Kimmich (Bayern Munich), Bastian Schweinsteiger (Manchester United), Julian Weigl (Borussia Dortmund)
Forwards: Thomas Muller (Bayern Munich), Andre Schurrle (Wolfsburg), Lukas Podolski (Galatasaray), Mario Gomez (Besiktas), Marco Reus (Borussia Dortmund), Leroy Sane (Schalke)