Were it not for the ups and downs already experienced over the past 17 months of trade frictions, it would no doubt have caused jitters when the US president warned on Tuesday that he would jack up tariffs substantially should the phase one deal with China fail to materialize.

Since the wolf did not come down on the fold at once, the world's expectations for a deal, large or small, are realistic. Anyone aware of the US administration's habits will appreciate that even if the deal is signed, it could be scrapped at any time on the whim of Washington.

Considering the US leader said on the weekend that reports suggesting some tariffs are to be removed were "incorrect", and the Chinese side's insistence that no deal is acceptable under additional tariffs, there is reason to believe that the US administration's superstitious faith in tariffs is once again close to killing a deal in the cradle.

That the two sides agreed to a phased negotiation is in itself a progress, as it is an effective means to focus their attention on the easiest issues first, which would establish a stable platform for negotiations on the more contentious issues between them.

Considering the optimism the two sides displayed last month, when they announced the breakthrough of their phase one deal, it seemed that it only required an opportunity for the two leaders to sit down together for it to be signed into effect. But a few weeks is a long time in this trade war, and it seems that the situation has now changed once more.

The big gap in their stance on tariffs seems to have put a spanner in the works, and the tariffs themselves have now become part of the to and fro over who does what for what. The Chinese Commerce Ministry said on Thursday that the two sides are holding "in-depth discussions" on canceling tariffs to push the first phase trade agreement over the finish line.

China has already exempted additional tariffs on many key US exports, including agricultural products, which set the stage for the mini deal they agreed on. But the US tariffs on $300 billion of Chinese imports have shown no sign of loosening, and Washington's threat of higher tariffs on the remaining $250 billion of Chinese goods still hangs over the negotiations.

In other words, although the two sides have found some things they can agree on, their wrangling over tariffs has just began, which will be a true test of their nascent rapprochement and their ability to untangle the knots of the complex issues that have them at loggerheads.

An end to the trade war would be good for all, but if the US refuses to budge on tariffs, the trade talks will undoubtedly rewind to where they were before the phase one deal was struck.