Monk was speaking after winger Montero was linked in the German media with Bayern Munich, while club captain Williams has also been the subject of speculation with Everton said to be keen on the defender should John Stones leave for Chelsea.
Monk, who steered Swansea to their best Premier League finish of eighth last season and has seen his team start well again with four points from the opening two games, pledged to keep his squad intact.
One player who is set to leave the Liberty Stadium though is Spanish striker Michu.
“It took me a long time to get the side to what I wanted it to be,” Monk said ahead of this Saturday’s match with Sunderland.
“We’re not the finished article but we’re getting nearer and nearer and this year is another step forward.
“To let that hard work go to waste would be criminal. This is the squad I want to go forward with and it is the squad we will go forward with, no-one is for sale and we’re looking forward to the season.
“Ask any one of those players and they’re looking forward to being with Swansea this season because we’re trying to create something here.”
Montero has been in superb form in the opening two matches of the season, giving Chelsea full-back Branislav Ivanovic a torrid time in a 2-2 draw at Stamford Bridge and impressing again in the 2-0 victory over Newcastle.
Monk feels the 25-year-old can still improve due to the increased competition on the Swansea training ground.
“Jeff’s done very well, he’s come back really positive like the whole squad,” Monk said.
“He’s had an excellent two games and hopefully he can be even better. He’s contributing magnificently the way he’s been playing, but they all are.”
Monk did suggest that the saga over Michu’s future could be drawing to an end.
The Spanish striker spent last season on loan at Napoli in Italy and, although the 29-year-old has a year left on his Swansea contract, both club and player accept that a parting of the ways is inevitable.
“This is why I’m at the stadium – I’ll be having a meeting with the chairman afterwards,” Monk said amid British newspaper reports linking Michu to Celtic.
“We’re negotiating with his representatives and there’s been different clubs supposedly, but there’s been nothing concrete at all.
“But it’s best for both parties – for Michu and the club itself – if we can find a solution.”