Donald Trump may struggle to tear himself away from the television on Wednesday, given public impeachment hearings get underway, but the U.S. president has a big meeting in the diary: Turkish President Recep Tayyip Erdogan is coming to the White House.

While the inquiry on Capitol Hill may dominate the news agenda, Erdogan's visit comes at an important – and tense – time in bilateral ties.

"Despite the fog in our relations, we are in agreement," the Turkish president said before flying to Washington, "with Mr Trump to improve our relations."

Here are five issues to watch:

1. Syria ceasefire and sanctions

Trump and Erdogan reached a controversial understanding in October whereby U.S. forces pulled out of northern Syria ahead of Turkish offensive into the region. The Turkish move was designed to create a safe zone to repatriate Syrian refugees and push back Kurdish groups from its border.

Erdogan said on Tuesday he would tell Trump he must do more to implement a ceasefire deal agreed on October 17. The agreement saw Turkey suspend its offensive in northern Syria in return for Washington ensuring a pullout of Syrian Kurdish forces from the proposed safe zone.

The House of Representatives has passed a sanctions package to punish Turkey over its Syria operation while a bipartisan group of senators have indicated they could also back sanctions. Questions are also likely to be asked as to why the U.S. has pursued the course it has. 

2. S-400 purchase, F-35 removal

A long-running row over the Turkish decision to buy Russia's S-400 missile defense system intensified this year, with Ankara – a NATO country – receiving its first deliveries of the hardware in July.

The U.S. has threatened – but not imposed – sanctions and removed Turkey from the F-35 fighter jet program, in which Ankara was a manufacturer and buyer. Both the U.S. and NATO have warned the stealth capabilities of the F-35 could be compromised. 

However in a letter last week, Trump is believed to have offered Erdogan a way to avoid the imposition of sanctions. That may involve Ankara not deploying the Russian system, but details of any possible agreement have not been released. If a deal isn't made, sanctions are likely. 

3. Trade and tariffs

Negotiations over a bilateral trade deal worth 100 billion U.S. dollars were stopped after Turkey's offensive in northern Syria began, and tariffs on Turkish steel were hiked to 50 percent.

The leaders have exchanged words over economic relations repeatedly over the past three years, with Trump going so far as to threaten to "swiftly destroy" the Turkish economy with sanctions.

However, Trump's latest letter to Erdogan suggests the trade deal is now on the table again. 

4. Extraditions and prosecutions

Trump and Erdogan clashed early on in the U.S. president's term over the detention of American pastor Andrew Brunson, who was on trial in Turkey on terrorism charges. 

Brunson was eventually released, but disputes over individuals in both countries continue. Washington wants charges against U.S. consular workers prosecuted in Turkey to be dropped, while Ankara continues to push an extradition request for U.S.-based Islamic cleric Fethullah Gulen, whom it blames for orchestrating the 2016 failed coup.

The House of Representatives' vote in favor of a non-binding resolution recognizing as genocide the deaths of 1.5 million Armenians 100 years ago, for the first time, has further angered Turkey.

5. Personal chemistry

White House officials told the Washington Post the White House meeting was part of a package offered to Turkey after a ceasefire deal was made. Given the scale of flashpoints in the relationship between the countries, some may be surprised the meeting between the leaders is going ahead at all. 

According to analysts, Trump and Erdogan's personal bond is keeping the relationship on track. Trump has frequently praised Erdogan since becoming president, describing him as a "tough guy who deserves respect" and a "hell of a leader".

"The Erdogan-Trump part of the U.S.-Turkey relationship is really the only component of it that is currently working right now," Soner Cagaptay, Turkish Research Program director at The Washington Institute for Near East Policy, told Reuters.

"Confidence between government agencies of both countries has eroded and there is considerable anger toward the U.S. in Turkey and vice versa.”

(With input from AFP, Reuters)