By Purvi Agarwal

Feb 19 (Reuters) - A rising dollar pressured most Latin American currencies on Wednesday as investors assessed U.S. President Donald Trump's latest tariff threats, while South African markets fell after the country's national budget was postponed.

MSCI's gauge of Latin American currencies .MILA00000CUS was down 0.4%, on track to snap a six-session winning streak. The stocks index .MILA00000PUS lost 1%.

In yet another round of threats, Trump said he intends to impose auto tariffs "in the neighborhood of 25%" and similar duties on semiconductors and pharmaceutical imports, following the duties on steel and aluminum imports announced earlier this month.

Trump had suspended his February 1 tariffs on Mexico and Canada, shortly after announcing them, following border security agreements with the two U.S. allies. This led investors to view the tariffs primarily as a negotiating tool.

Initial optimism around developments in the U.S.-Russia relationship and delayed U.S. tariffs faded, giving way to a slightly higher dollar =USD.

"The sentiment on the USD has become a little more moderate, as many in the market see potential pathways to a weaker dollar under Trump, but no one seems willing to commit to the idea just yet," said Brad Bechtel, global head of FX at Jefferies.

The Mexican peso MXN= led declines with a 0.8% fall. Colombia's peso COP= lost 0.1%, with higher oil prices limiting its declines.

Meanwhile, South Africa's rand ZAR= weakened 0.9% after the government's national budget was postponed at the last minute because of a disagreement between the political parties in the ruling coalition.

The delay triggered the sharpest selloff in the country's government bonds since December, with the 2052 maturity US836205BE37=TE down as much as 1 cent.

The benchmark 2030 government bond ZAR2030= also was weaker, with the yield up 6.5 basis points at 9.19%. Stocks .JTOPI fell 0.3%.

"(The delay) suggests that it is domestic rather than foreign policy where the cracks in the coalition lie ... the government of national unity's fragility will make fiscal consolidation and structural efforts even harder to push through," said David Omojomolo, Africa economist at Capital Economics.

Brazil's real BRL= was flat. Former Brazilian President Jair Bolsonaro was charged with leading a plot to overthrow the government after his 2022 election loss.

Chile's peso CLP= was off 0.4%, as copper prices eased.

However, J.P. Morgan said equity markets in Argentina and Turkey could post returns of more than 20% this year, driven by policy reforms aimed at reducing inflation levels.

Developments in the Russia-Ukraine conflict and the ceasefire between Israel and Hamas also were being watched, alongside the minutes of the U.S. Federal Reserve's last meeting, which are due to be released at 2 p.m. EST (1900 GMT).

Argentina's Merval stock index .MERV fell 1.1%, and indexes in Brazil .BVSP and Mexico .MXX fell 0.7% and 0.8%, respectively.

Separately, S&P Global Ratings revised its policy rate forecasts for 2025 and 2026 for nine key emerging markets, including Brazil and Mexico, with a median shift of 50 basis points higher.

Highlights:

** China promises Latin America 'trustworthy' ties as Trump lays out demands

** China unveils action plan to stabilise foreign capital

** Polish consumer sentiment improves in Feb, but worries about future rise

** Brazil raises $2.5 billion with 6.75% yield in global bond sale with 10-year dollar issuance

Key Latin American stock indexes and currencies at 1505 GMT:

(Reporting by Purvi Agarwal in Bengaluru; Editing by Paul Simao)

((Purvi.Agarwal@thomsonreuters.com;))