The Washington Post says the United States has stepped up diplomatic pressure on China following North Korea’s artillery attack on South Korea’s Yeonpyeong Island last month.

The paper quoted a senior U.S. administration official as saying that the U.S. is applying such pressure on Beijing by accusing its leaders of "enabling" North Korea to start a uranium-enrichment program and to launch attacks on South Korea.

According to the paper, another senior U.S. official added that “the Chinese embrace of North Korea in the last eight months has served to convince North Korea that China has its back and has encouraged it to behave with impunity.”

Meanwhile, the New York Times said that tension between the U.S. and China has been mounting since the North’s artillery attack. The report noted that it took 13 days for U.S. President Barack Obama and Chinese President Hu Jintao to have a conversation about North Korea’s attack.