(Reuters) - U.S. President Donald Trump appears before the United Nations General Assembly on Tuesday in the midst of challenges worldwide dogging his presidency.

U.S. President Donald Trump speaks during a meeting on the sidelines of the annual United Nations General Assembly in New York City, New York, U.S., September 23, 2019. REUTERS/Jonathan Ernst

The following are some facts about his diplomatic efforts:

IRAN

Trump finds himself in a diplomatic minefield of his own making after Sept. 14 attacks on Saudi oil facilities that the United States and its allies have blamed on Iran. Tehran denies involvement.

An overt military strike on Iran might deter it from further actions but runs the risk of escalation or Iranian retaliation anywhere from Afghanistan to Israel.

Tensions have increased between the two countries since May 2018 when Trump withdrew from a 2015 international nuclear accord with Iran and ramped up sanctions.

A negotiation would require Washington to make some kind of concessions to Tehran, something U.S. officials have not ruled out but clearly do not want.

Failing to do either could convince Iran it can keep hitting Gulf infrastructure and raising oil and gas prices, something Trump does not want before his 2020 reelection campaign.

As a result, Trump could choose a covert response - possibly by using cyber tools to destroy Iranian oil infrastructure - and signal that Iran will pay a price for its suspected involvement in attacks on tankers, U.S. drones and Saudi facilities.

NORTH KOREA

Trump has held two summits with North Korean leader Kim Jong Un over the past 16 months, one in Singapore and the other in Hanoi, but the two leaders have yet to reach an agreement on Kim giving up his nuclear weapons in exchange for a lifting of economic sanctions.

Now there is talk about a third summit, an idea being pushed by South Korean President Moon Jae-in. Meeting Moon on Monday, Trump said he was open to a third summit but would like to know what would come out of it.

“I want to know what’s going to be coming out of it,” he told reporters.

This is a change from Trump’s past belief that the simple act of meeting can lead to breakthroughs without trying to negotiate an agreement ahead of time.

CHINA

Trump’s biggest objective is to seal a trade deal with China that would break down barriers to trade and include safeguards to protect American intellectual property and stop the forced transfer of American technology to Chinese companies.

Despite multiple meetings by trade negotiators, a broad agreement has been elusive.

This has led to suspicions from Republican Trump that Chinese President Xi Jinping is trying to wait until the November 2020 presidential election to see if Trump gets defeated by a Democratic candidate who might be more lenient toward Beijing.

The United States finds itself increasingly at odds with China on an array of issues besides trade. A Chinese military buildup has worried U.S. defense officials along with Chinese attempts to extend its influence in the South China Sea and its crackdown on the Uighurs, the Muslim minority in Xinjiang.

VENEZUELA

Trump’s efforts to force the ouster of socialist Venezuelan President Nicolas Maduro through sanctions and muscular rhetoric have not yet led to the departure of Maduro, whose 2018 re-election was considered fraudulent by the Venezuelan opposition.

Trump and U.S Secretary of State Mike Pompeo were expected to attend a meeting with Western Hemisphere leaders to discuss Venezuela on Wednesday.

Opposition leader Juan Guaido has been recognized as Venezuela’s rightful leader by the United States and most Western countries, but Maduro retains the recognition of the 193-member U.N. General Assembly.

Maduro calls Guaido a U.S.-backed puppet seeking to oust him in a coup.

Trump imposed a freeze on all Venezuelan government assets in the United States in August, sharply increasing economic and diplomatic pressure on Maduro.