If you're aiming to build a strong investment portfolio, then it is usually a good idea to include a few blue chips in there.

But which blue chip ASX 200 stocks could be buys in January? Here are three no-brainer picks that are rated highly by analysts:

CSL Ltd (ASX: CSL)

The first ASX 200 blue chip stock that could be a buy in January is biotechnology giant CSL.

The team at Bell Potter is very positive on the company. This is due largely to its positive margin outlook, which is being underpinned by the key CSL Behring business. The broker also feels that its shares are attractively priced based on historical multiples. It explains:

CSL presents an attractive buying opportunity as we anticipate the start of a margin recovery phase for CSL, driving above-market earnings growth over the next few years. CSL trades at a 12-month forward PE of ~28x, representing a discount to its 10-year average of ~31x. Furthermore, the company will continue to deleverage the balance sheet over the next few years. Given the company's proven quality and growth prospects, we believe significant upside remains.

Bell Potter has a buy rating and $345.00 price target on its shares.

Nextdc Ltd (ASX: NXT)

Another ASX 200 blue chip stock that could be a buy is data centre operator NextDC.

The team at Morgans is very positive on the company. This is due largely to its exposure to the artificial intelligence (AI) megatrend. It explains:

Digital Realty recently reported a record sales quarter during which it sold double the data centre capacity of its previous high and about four times more capacity than it usually sells in a quarter.  This reinforces our view that the significant demand for cloud computing and AI-related digital infrastructure is going to unpin attractive returns and long-term growth.

Our preferred exposure is NEXTDC. It has 17 operational data centres in Australia and nearly a dozen under construction or about to be built across Australasia and Asia.

Morgans currently has an add rating and $20.50 price target on its shares.

Woolworths Limited (ASX: WOW)

Woolworths could also be an ASX 200 blue chip stock to buy now according to Goldman Sachs. It is of course Australia's largest retailer and one of the country's big two supermarket operators.

The broker believes that Woolworths has an advantage over its rivals that its online operations. It said:

We believe WOW has the strongest advantage in winning the digital consumer, with the highest amount of foot traffic to digital assets vs. key peers, the broadest store footprint, and the highest e-Comm penetration. We continue to believe WOW has a multi-year advantage in terms of scale and industry knowledge vs. key industry peers that will help to better insulate it against Amazon risk vs. peers.

Goldman currently has a buy rating and $36.20 price target on its shares.