(Adds comments by Mnuchin, Larry Kudlow)
By Susan Heavey and Jeff Mason
WASHINGTON, July 15 (Reuters) - U.S. President Donald Trump on Monday seized on slowing economic growth in China as evidence that U.S. tariffs were having "a major effect" and warned that Washington could pile on more pressure as bilateral trade talks sputtered along.
Data released earlier on Monday showed growth in the world's second-largest economy had slowed to 6.2% in the second quarter, its weakest pace in at least 27 years, amid ongoing trade pressure from the United States.
"This is why China wants to make a deal with the U.S., and wishes it had not broken the original deal in the first place," Trump tweeted.
U.S. Treasury Secretary Steven Mnuchin later said he and U.S. Trade Representative Robert Lighthizer would speak with their Chinese counterparts by phone again this week as part of the recently resumed trade talks. A face-to-face meeting hinges on progress in the year-long trade war, he added.
"To the extent that we make significant progress, I think there's a good chance we'll go there later," he told reporters at a rare White House news briefing ahead of his trip to meet with finance ministers from the Group of Seven (G7) nations.
Trump and Chinese President Xi Jinping last month agreed to another truce in the year-long trade spat between the world's two largest economies. That agreement, announced after the leaders of the world's two largest economies met in Osaka, Japan, was aimed at kickstarting stalled negotiations, but no deadline has been set for the process to conclude.
Trump has grown increasingly frustrated that China has not delivered on what he viewed as a promise by the Chinese side to start buying more U.S. agricultural goods, even as talks continued.
White House economic adviser Larry Kudlow told Fox Business Network the administration was still waiting for Beijing to reciprocate for goodwill gestures such as eased restrictions on China's Huawei Technologies Co Ltd and a freeze in any new tariffs.
"We expect the Chinese to be launching a significant purchase of U.S. agriculture products, goods and services. We haven't seen that quite yet, but we're very keenly watching the developments there," he said.
However, sources familiar with the state of negotiations insist the Chinese side did not make firm commitments at the meeting to immediately purchase agricultural commodities.
Adding to mounting pressure on China, Trump will sign an order on Monday seeking to increase the U.S. domestic content threshold for iron and steel in federal procurements, White House trade adviser Peter Navarro said on Fox News.