The main index added 1pc, as internationally exposed firms such as HSBC and AstraZeneca rose and offset a 32pc plunge in Micro Focus after the IT group warned on its full-year revenue.
The FTSE 250 midcap index ended up 0.4pc, with gains capped due to a more than 50pc drop in consumer credit provider Amigo Holdings following an annual forecast cut.
Following a subdued start to the session earlier in the day, investor sentiment swiftly picked up as China's commerce ministry said Beijing and Washington were discussing face-to-face trade talks that were scheduled to be held in September.
The news was a welcome relief to stock markets, which have seen the trade dispute stoke fears of an impending recession in recent weeks.
The FTSE 100 is still on course for its sharpest monthly drop in four years.
"The unfortunate reality is that these comments are likely more hot air but with everything that's happening at the moment, they do provide rays of hope," said Oanda senior market analyst Craig Erlam.
Constituents of the exporter-heavy FTSE 100 also found support in a drop in sterling value after Prime Minister Boris Johnson's plan to suspend parliament. The move has enraged his opponents as it limits the time available to prevent Britain crashing out of the European Union without a deal in October.
"The calculation here would be that the Prime Minister is taking a high stakes gamble on forcing a vote of no confidence and daring MPs to push him towards calling a general election," CMC Markets analyst Michael Hewson said.
Among single stocks, technology company Smiths Group was the biggest riser among bluechips after Goldman Sachs raised its rating on the stock.
Mid-cap Tullow Oil fell 5.1pc after the oil and gas explorer said its plan to sell another stake in a Uganda project has been called off due to a tax dispute with the Ugandan authorities.
At the other end of the spectrum, oilfield service provider Hunting jumped 5pc on its best day since January as strong activity in the United States drove demand for its equipment, thereby boosting earnings.