China is pursuing one of its most ambitious overseas takeover attempts yet, as China National Chemical Corp. nears an agreement to buy Swiss pesticide and seed giant Syngenta AG for roughly $43 billion, according to people familiar with the matter. As WSJ's Rick Carew, Shayndi Raice and Eyk Henning report:

These people said an agreement between the two companies could be announced as soon as Wednesday, but also cautioned that talks could still fall apart. If an agreement is reached, it would be just the start of what could be a fraught process gaining government and regulatory approval around the world, including...